Keynote lectures/Minerals

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This image shows several amphibole crystals in a glass bowl. Credit: Karelj.

Minerals are usually solid, inorganic substances of natural occurrence.

Chemicals[edit | edit source]

Cubic zirconia crystal made by Shelby Gem Factory. Credit: Doug Coldwell.

Chemicals is a lecture on the general nature and specific characteristics of various natural and hominin-made substances. It is an offering from the school of chemistry.

Def. any "specific[1] [...] element or[2] [...] compound[1] or alloy"[3] is called a chemical.

Materials[edit | edit source]

The image above contains clickable links
A variety of wood samples are tiled.

Def. matter "which may be shaped or manipulated, particularly in making something"[4] is called a material.

On the right are displayed tiles of naturally occurring materials. Wood is a mineraloid.

Rocks[edit | edit source]

Rock outcrop occurs along a mountain creek near Orosí, Costa Rica. Credit: .

Rocks are a bound aggregate of minerals with usually a large geographic extent.

Occasionally, a rock is composed of only one mineral. But a crystal of the mineral fluorite in your hand is a stone rather than a rock.


  1. a "naturally occurring aggregate of minerals"[5]
  2. a naturally occurring aggregate of solid mineral matter that constitutes a significant part of the earth's crust or
  3. any natural material with a distinctive composition of minerals

is called a rock.

Def. full of, or abounding in, rocks; consisting of rocks is called rocky.

Petrology[edit | edit source]

The photomicrographs show of a sand grain held in an amorphous matrix, in plane-polarized light on top, cross-polarized light on bottom. Scale box in mm. Credit: Qfl247.
This is a photomicrograph of a thin section of gabbro. Credit: Siim Sepp.
This photomicrograph is of a thin section of a limestone with ooids. The largest is approximately 1.2 mm in diameter. Credit: Photograph taken by Mark A. Wilson (Department of Geology, The College of Wooster).
This is a thin section with cross-polarized kight through a sand-sized quartz grain of 0.13 mm diameter. Credit: Glen A. Izett, USGS.
This is a thin section of a shocked quartz grain. Credit: Martin Schmieder.

Def. the study of the origin, composition and structure of rock is called petrology.

Def. a section formed by a plane cutting through an object, usually at right angles to an axis is called a cross section.

Def. a laboratory preparation of a rock, mineral, soil, pottery, bones, or metal sample for use with a polarizing petrographic microscope, electron microscope and electron microprobe is called a thin section.

At lower left is a thin section through a sand-sized quartz grain "from the USGS-NASA Langley core showing two well-developed, intersecting sets of shock lamellae produced by the late Eocene Chesapeake Bay bolide impact. This shocked quartz grain is from the upper part of the crater-fill deposits at a depth of 820.6 ft in the core. The corehole is located at the NASA Langley Research Center, Hampton, VA, near the southwestern margin of the Chesapeake Bay impact crater."[6] "Very high pressures produced by strong shock waves cause dislocations in the crystal structure of quartz grains along preferred orientations. These dislocations appear as sets of parallel lamellae in the quartz when viewed with a petrographic microscope. Bolide impacts are the only natural process known to produce shock lamellae in quartz grains."[6]

Lower right shows another thin section in plane polarized light of a shocked quartz grain with two sets of decorated planar deformation features (PDFs) surrounded by a cryptocrystalline matrix from the Suvasvesi South impact structure, Finland.

In a specimen of shocked quartz, stishovite can be separated from quartz by applying hydrogen fluoride (HF); unlike quartz, stishovite will not react.[7]

Petrography[edit | edit source]

Def. the scientific description and classification of rocks is called petrography.

Mineralogy[edit | edit source]


  1. the scientific study of minerals or
  2. "a science dealing with minerals, their crystallography, physical and chemical properties, classification, and the ways of distinguishing them"[8]

is called mineralogy.

Physical properties[edit | edit source]

Hardness[edit | edit source]

Def. a "scale of the hardness of minerals based on their ability to scratch one another"[9] is called Mohs scale.

Mohs hardness Mineral Chemical formula Absolute hardness[10] Image
1 Talc Mg3Si4O10(OH)2 1 Talc block.jpg
2 Gypsum CaSO4·2H2O 3 Gypse Arignac.jpg
3 Calcite CaCO3 9 Calcite-sample2.jpg
4 Fluorite CaF2 21 Fluorite with Iron Pyrite.jpg
5 Apatite Ca5(PO4)3(OH,Cl,F) 48 Apatite Canada.jpg
6 Orthoclase KAlSi3O8 72 OrthoclaseBresil.jpg
7 Quartz SiO2 100 Quartz Brésil.jpg
8 Topaz Al2SiO4(OH,F)2 200 Topaz cut.jpg
9 Corundum Al2O3 400 Cut Ruby.jpg
10 Diamond C 1600 Rough diamond.jpg

A porcelain streak plate has a hardness of 7.0.

Def. the "color of the powder of a mineral. So called, because a simple field test for a mineral is to streak it against unglazed white porcelain."[11] is called a streak, or streak test.

Densities[edit | edit source]

Def. a measure of the mass of matter contained by a unit volume is called a density.

To measure the density of a mineral crystal that does not dissolve in distilled water, pour a specific number of milliliters (mls) of distilled water into a milliliter-graduated cylinder, weigh the crystal to obtain its mass in grams (gm), carefully immerse the crystal in the water and gently agitate to eliminate air bubbles, take the difference between the final number of milliliters from the initial number to obtain the amount of water displaced.

Liquid distilled water at one atmosphere and 0°C has a density of 999.8395 kg/m3. At 25°C, 997.0479 kg/m3. Using 1 gram/cm3 = 1000 kg/m3 and 1 ml of distilled water at one atmosphere and 25°C equals 1 cm3, each displaced ml in cm3 divided into the mineral crystal mass in gms becomes the mineral crystal density.

Fluorescences[edit | edit source]

This image exhibits forty-seven minerals that fluoresce in the visible while being irradiated in the ultraviolet. Credit: Hannes Grobe Hgrobe.
Halite shows green fluorescence. Credit: Ra'ike.

Def. the "emission of light (or other electromagnetic radiation) by a material when stimulated by the absorption of radiation or of a subatomic particle"[12] is called fluorescence.

Transmissivity[edit | edit source]

Comparisons of 1. opacity, 2. translucency, and 3. transparency; where behind each panel is a star, are shown. Credit: Anynobody.

Def. the property that light passes through it almost undisturbed, such that one can see through it clearly is called transparency.

Def. the property that light passes through a mineral but detailed images do not is called translucency.

Def. not "allowing light to pass through"[13] is called opaque.

Reflectivity[edit | edit source]

Percentage of diffusely reflected sunlight is shown in relation to various surface conditions. Credit: Wereon.
Diffuse and specular reflection can occur from a glossy surface.[14] The rays represent luminous intensity the reflectivity of which varies uniformly for an ideal diffuse reflector. Credit: GianniG46.
The image shows cherry tree resin. Credit: Darkone.
This piece of polished amber, a resin, exhibits a resinous luster. Credit: Oxfordian Kissuth.
The image shows a glassy or vitreous building. Credit: Bjs.

Def. hue of a smooth surface of a mineral exhibited when sunlight reflects is called its color.

Def. the fraction of incident light or radiation reflected by a surface or body, commonly expressed as a percentage is called an albedo.

Def. reflectivity pertaining "to mirrors; mirror-like"[15] is called specular reflectivity.

Def. shine, "polish or sparkle"[16] is called luster, or lustre.

Def. the manner in which the surface of a mineral reflects light is called luster.

Def. having a shine, polish or sparkle comparable to resin is called a resinous luster, or is resinous.

Def. "in particular smooth and (partly) reflective"[17] is called vitreous, or glassy.

Def. "having a matte [diffuse] finish or no particular luster or brightness"[18] is called a dull luster.

Def. luster made "of, appearing to be made of, resembling, or related to metal"[19] is called a metallic luster.

Def. a luster, or reflectivity, "to maximize light return"[20] is called a brilliant luster.

Magnetism[edit | edit source]

Mineral magnetite (lodestone), from Tortola, British Virgin Islands is magnetic. Credit: Chris Oxford.

Def. a mineral that is weakly attracted by the poles of a magnet but does not retain any permanent magnetism is called a paramagnet, or a paramagnetic mineral.

Def. a mineral that is weakly attracted by the poles of a magnet tending to become magnetized in a direction at 180° to the applied magnetic field but does not retain any permanent magnetism is called a diamagnet, or a diamagnetic mineral.

Def. a mineral that is exhibits the poles of a magnet even in zero applied magnetic field is called a ferromagnet, or a ferromagnetic mineral.

Def. a mineral that is exhibits the poles of a magnet even in zero applied magnetic field but with opposite directions is called a antiferromagnet, or a antiferromagnetic mineral.

Def. a mineral that is exhibits the poles of a magnet even in zero applied magnetic field with opposite directions but a net magnetic moment is called a ferrimagnet, or a ferrimagnetic mineral.

Chemical properties[edit | edit source]

Many chemical elements occur naturally as minerals, often called native, such as native gold.

Some native elements occur with others as natural alloys.

The majority of chemical elements occur naturally in compounds.

The inert gases occur naturally as decay products of radioactivity and as atoms trapped inside mineral crystals or beneath impermeable rock.

Inductively coupled plasma mass spectrometry[edit | edit source]

Inductively coupled plasma mass spectrometry (ICP-MS) ionizes a small mineral sample and uses a mass spectrometer to separate and quantify the ions. ICP-MS scans for all elements from lithium to uranium in a mineral sample simultaneously.

Atomic absorption spectroscopy[edit | edit source]

Atomic absorption spectrometer block diagram shows the features of the technique. Credit: K05en01.

Flames and electrothermal (graphite tube) atomizers are usually used to drive atoms off a small mineral sample.

Each of the above two techniques may be useful for obtaining the best quantification of the elements present in a mineral sample.

Flame emission spectroscopy[edit | edit source]

A flame is created during the assessment of calcium ions in a flame photometer. Credit: Panek.
This image shows the flame test for Rubidium. Credit: Didaktische.Medien.

In flame emission spectroscopy, as shown in the image on the right, a small mineral sample is put into the flame as either a gas, sprayed solution, or on a small loop of wire, usually platinum. The flame evaporates the mineral and breaks chemical bonds to create free atoms. Each element emits light at a characteristic wavelength. These emissions are dispersed by a grating or prism and detected in the spectrometer.

If a Bunsen burner is available where you are trying to chemically analyze a mineral sample, inserting a small piece safely in the flame could prove helpful as the second image down on the right shows.

Symbol Name Color Image
Al Aluminium Silver-white, in very hot such as an electric arc, light blue Aluminum flame.png
As Arsenic Blue FlammenfärbungAs.jpg
B Boron Bright green FlammenfärbungB.png
Ba Barium Pale/Apple green Barium flame.png
Be Beryllium White
Bi Bismuth Azure
Ca Calcium Orange FlammenfärbungCa.png
Cd Cadmium Brick red
Ce Cerium Blue
Co Cobalt Silver-white
Cr Chromium Silver-white
Cs Caesium Blue-Violet Caesium flame.png
Cu(I) Copper(I) Bluish-green Copper (I) blue flame.png
Cu(II) Copper(II) (non-halide) Green Flame test on copper sulfate
Cu(II) Copper(II) (halide) Blue-green Cu+2 (CuCl2)-Blue.jpg
Ge Germanium Pale blue
Fe(II) Iron(II) Gold, when very hot such as an electric arc, bright blue, or green turning to orange-brown
Fe(III) Iron(III) Orange-brown An iron (III) flame, generated using the thermite reaction
Hf Hafnium White
Hg Mercury Red
In Indium Indigo/Blue
K Potassium Lilac Potassium flame.png
Li Lithium crimson red; invisible through green glass FlammenfärbungLi.png
Mg Magnesium (none), but for burning Mg metal Intense White Mg-flame.jpg
Mn (II) Manganese (II) Yellowish green
Mo Molybdenum Yellowish green
Na Sodium Intense yellow; invisible through cobalt blue glass Flametest--Na.swn.jpg
Nb Niobium Green or blue
Ni Nickel Silver-white (sometimes reported as colorless)
P Phosphorus Pale bluish green
Pb Lead Blue/white FlammenfärbungPb.png
Ra Radium Crimson red Radium flame.png
Rb Rubidium Red-violet Die Flammenfärbung des Rubidium.jpg
Sb Antimony Pale green FlammenfärbungSb.png
Sc Scandium Orange
Se Selenium Azure blue
Sn Tin Blue-white
Sr Strontium Crimson to Scarlet, yellowish through green glass and violet through blue cobalt glass Strontium flame.png
Ta Tantalum Blue
Te Tellurium Pale green
Ti Titanium Silver-white
Tl Thallium Pure green Thallium flame.png
V Vanadium Yellowish Green
W Tungsten Green
Y Yttrium Carmine, Crimson, or Scarlet
Zn Zinc Colorless (sometimes reported as bluish-green) Zinc burning.JPG
Zr Zirconium Mild red

From a flame analysis of a small mineral sample that easily dissolved in water, the chemical sodium was detected.

"Halide ions in solutions are detected using silver nitrate solutions. The test solution is acidified using a few drops of dilute nitric acid, and then a few drops of silver nitrate solution are added. Different coloured silver halide precipitates form, depending on the halide ions present:"[21]

  • chloride ions give a white precipitate of silver chloride
  • bromide ions give a cream precipitate of silver bromide
  • iodide ions give a yellow precipitate of silver iodide

Crystallography[edit | edit source]


  1. an "experimental science of determining the arrangement of atoms in solids"[22], or
  2. the "study of crystals"[22] is called crystallography.

Formula units[edit | edit source]

This is a model of how NaCl formula units could form a cube. Credit: BruceBlaus.
Illustration shows the close-packing of equal spheres in both hcp (left) and fcc (right) lattices. Credit: Twisp.

Flame emission spectroscopy of a test mineral described in the above section suggests some conclusions about the mineral.

The halide present was chlorine. The mineral is most likely halite. The formula unit is NaCl. The mineral grains appear to be cuboidal. At the left is a model of how NaCl formula units could form a cube.

When NaCl is dissolved in water, it has the formula [Na(H2O)8]+. The chloride ion is surrounded by an average of 6 molecules of water.[23] As the water evaporates, the cations of sodium and the anions of chlorine should be drawn back together.

If the sodium and chlorine ions can be represented by equal-sized hard balls, they would be expected to form close-packed solids.

An examination of the two types of close-packed structures shows a problem that may disqualify such structures for representing NaCl. Each sphere is the same distance from every other sphere. An effort to use some as sodiums and the others as chlorines always results in at least two sodiums contacting each other and the same thing happens with the chlorines.

Models[edit | edit source]

This is a body-centered cubic unit cell. Credit: Baszoetekouw.
Crystal structure of NaCl shows coordination polyhedra. Credit: Solid State.
Relative radii of atoms and ions for neutral atoms colored gray, cations red, and anions blue. Credit: Popnose.

A slightly more open structure is the body-centered cubic shown in the image on the left. Here, one sodium ion could be surrounded by six chlorines in an octahedron, and one chlorine anion could be surrounded by six sodium cations. These are shown in the second image down on the left.

Using the approximate ionic radii from the third image down on the right for Na+ as 116 pm and 167 pm for Cl- to calculate a radius ratio yields 0.695. Such a size ratio falls in the octahedron range of ≥ 0.414 and < 0.732.

The ball and stick model on the left shows what's inside the cube.

Habits[edit | edit source]

The image shows that halite can occur in a massive habit. Credit: Helix84.

Def. form "of growth or general appearance of a variety or species of plant or crystal"[24] is called a habit.

The image on the left shows that halite can occur in a massive habit but is apparently always crystalline.

Cleavages[edit | edit source]

Image shows a mineral specimen of Halite. Credit: Vassia Atanassova - Spiritia.

The image on the right shows a more familiar crystal habit of halite.

Halite might be expected to break leaving behind a cube-like face.

Def. the "tendency of a crystal to split along specific planes"[25] is called cleavage.

The cleavage described for halite is "{001} perfect Fracture conchoidal. Brittle."[26]

Unit cells[edit | edit source]

This is a possible unit cell for crystalline NaCl. Credit: Ed Caruthers.

Def. the "smallest repeating structure (parallelepiped) of atoms within a crystal, from which the structure of the complete crystal can be inferred"[27] is called a unit cell.

An examination of the model unit cell for crystalline NaCl shows a repeat pattern along the left front edge starting with a Cl atom at the corner. Moving along the line of atoms at this lowest edge, next is a smaller Na atom, then another Cl atom. This second Cl atom is a repeat of the first.

Going back to the corner Cl atom and moving straight up above it is a Na atom. Above that Na atom is again another Cl that is another repeat of the first.

Looking at the eight corners of this perspective view of the model there is a Cl atom at each corner. Starting again at the lower left corner Cl, directly behind the left rear face of this unit cell is another such unit cell not shown. Further left of these two unit cells are two more. One is along the base diagonal though the corner Cl and the second is in front sharing the face of the model unit cell shown. Counting the model shown there are four unit cells in this layer that share the lower left corner Cl atom.

Right below this layer of four unit cells are four identical unit cells all cornered to this same Cl atom in the lower left corner of the model. Summarizing, the corner of a unit cell is shared by eight unit cells total.

From visualizing nearer unit cells next to the one drawn, an edge of this cell is shared by four unit cells, and each face by two unit cells.

Looking at the numbers of Cls and Nas:

  1. eight corner Cls are each shared by eight unit cells so one corner Cl per unit cell,
  2. along each edge between each corner Cl is a Na, each of 12 edges is shared by four unit cells, so 3 Nas per unit cell,
  3. each face shares a centered Cl with two unit cells, 6 such Cls, each shared by two unit cells, is 3 Cls,
  4. inside the unit cell pictured there is one and only one Na, shared with no other unit cell, so one Na,

totalling the anions, there are 4 Cls, totalling the cations there are 4 Nas. In a unit cell for this model of halite, there are four formula units. The formula content of a unit cell is often denoted as Z. For this model, Z = 4.

Visual crystallography[edit | edit source]

The image shows an example of Mitscherlich's goniometer. Credit: Samuel Orgelbrand's Universal Encyclopedia.

Classifications[edit | edit source]

The Strunz classification is based on the Dana system, but combines both chemical and structural criteria, the latter with regards to distribution of chemical bonds.[28]

As of November 2018, 5,389 mineral species are approved by the IMA.[29] They are most commonly named after a person (45%), followed by discovery location (23%); names based on chemical composition (14%) and physical properties (8%) are the two other major groups of mineral name etymologies.[28]

As the composition of the Earth's crust is dominated by silicon and oxygen, silicate elements are by far the most important class of minerals in terms of rock formation and diversity. However, non-silicate minerals are of great economic importance, especially as ores.[28]

The largest grouping of minerals by far are the silicates; most rocks are composed of greater than 95% silicate minerals, and over 90% of the Earth's crust is composed of these minerals.[28] Other common elements in silicate minerals correspond to other common elements in the Earth's crust, such as aluminium, magnesium, iron, calcium, sodium, and potassium.[28]

Inosilicates contain two important rock-forming mineral groups; single-chain silicates are most commonly pyroxenes, while double-chain silicates are often amphiboles.[30] Higher-order chains exist (e.g. three-member, four-member, five-member chains, etc.) but they are rare.[31]

Pyroxenes are common in the Earth's crust (about 10%) and are a key constituent of mafic igneous rocks.[28]

Amphiboles have great variability in chemistry, described variously as a "mineralogical garbage can" or a "mineralogical shark swimming a sea of elements"; the backbone of the amphiboles is the [Si8O22]12−; it is balanced by cations in three possible positions, although the third position is not always used, and one element can occupy both remaining ones; the amphiboles are usually hydrated, that is, they have a hydroxyl group ([OH]), although it can be replaced by a fluoride, a chloride, or an oxide ion.[28]

Because of the variable chemistry, there are over 80 species of amphibole, although variations, as in the pyroxenes, most commonly involve mixtures of Ca2+, Fe2+ and Mg2+.[28]

The non-silicates have great economic importance, as they concentrate elements more than the silicate minerals do.[28]

Identifying and distinguishing[edit | edit source]

Theoretical minerals[edit | edit source]

Def. any "naturally occurring inorganic material that has a (more or less) definite chemical composition and characteristic physical properties"[32] is called a mineral.

Here's a theoretical definition:

Def. any naturally occurring usually inorganic substance that has a (more or less) definite chemical composition and a crystal structure is called a mineral.

Silicate minerals[edit | edit source]

This is a naturally occurring collection of intergrown feldspar crystals. Credit: Dave Dyet.

Silicate minerals are those with more atomic percent silicon oxide than other constituent elements.

For example, kaolinite is Al2Si2O5(OH)4. If aluminum (Al) at two atoms per molecular unit were the most numerous element, kaolinite would be an aluminide.

As the most numerous element is oxygen at 9 for 52.9 at %, kaolin is an oxide. The crystal structure consists of a sheet of interconnected silica tetrahedra. So, kaolin is a phyllosilicate.

Def. the "oxyanion of silicon SiO32- or any salt or mineral containing this ion"[33] is called a metasilicate.

Def. "any simple silicate mineral in which the SiO4 tetrahedra are isolated and have metal ions as neighbours"[34] is called a neosilicate.

Def. a "type of silicate crystal structure characterized by the linking of SiO4 tetrahedra through other cations rather than the sharing of oxygens among SiO4 tetrahedra"[26] is called a nesosilicate.

Def. "any salt or ester of orthosilicic acid, (M+)4SiO44− or Si(OR)4"[35] or "any silicate mineral, such as garnet or olivine, in which the SiO4 tetrahedra do not share oxygen atoms with each other"[35] is called an orthosilicate.

Def. any group of silicates that have structurally isolated double tetrahedra (the dimeric anion Si2O76-)[36] is called a sorosilicate.

Def. any group of silicates that have a ring of linked tetrahedra is called a cyclosilicate.

Def. "any silicate having interlocking chains of silicate tetrahedra"[37] is called an inosilicate.

Def. any "silicate mineral having a crystal structure of parallel sheets of silicate tetrahedra"[38] is called a phyllosilicate.

Def. type "of silicate crystal structure characterized by the sharing of all SiO4 tetrahedral oxygens resulting in three-dimensional framework structures"[26] is called a tektosilicate.

Def. any "of various silicate minerals ... with a three-dimensional framework of silicate tetrahedra"[39] is called a tectosilicate.

Alpha quartzes[edit | edit source]

Def. a continuous framework tectosilicate of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall [chemical] formula [of] SiO2 ... [of] trigonal trapezohedral class 3 2, usually with some substitutional or interstitial impurities, is called α-quartz.

When the concentration of interstitial or substitutional impurities becomes sufficient to change the space group of a mineral such as α-quartz, the result is another mineral. When the physical conditions are sufficient to change the solid space group of α-quartz without changing the chemical composition or formula, another mineral results.

Shocked quartz is associated with two high pressure polymorphs of silicon dioxide: coesite and stishovite. These polymorphs have a crystal structure different from standard quartz. Again, this structure can only be formed by intense pressure, but moderate temperatures. High temperatures would anneal the quartz back to its standard form.

Beta quartzes[edit | edit source]

Beta quartz (β-Quartz) is stable "between 573° and 870°C".[26]

Seifertites[edit | edit source]

Def. a polymorph of α-quartz formed at an estimated minimum pressure of 35 GPa up to pressures above 40 GPa with a orthorhombic space group Pmmm no. 47 is called seifertite.

Tridymites[edit | edit source]

Specimen consists of "porcelainite" - a semivitrified chert- or jasper-like rock composed of cordierite, mullite and tridymite, admixture of corundum, and subordinate K-feldspar. Credit: John Krygier.

Def. a polymorph of α-quartz formed at temperatures from 22-460°C with at least seven space groups for its forms with tabular crystals is called tridymite.

Coesites[edit | edit source]

Alpha-quartz (space group P3121, no. 152, or P3221, no. 154) under a high pressure of 2-3 gigapascals and a moderately high temperature of 700°C changes space group to monoclinic C2/c, no. 15, and becomes the mineral coesite.

Coesite is "found in extreme conditions such as the impact craters of meteorites".[40]

Stishovites[edit | edit source]

Def. a polymorph of α-quartz formed by pressures > 100 kbar or 10 GPa and temperatures > 1200 °C is called stishovite.

Stishovite may be formed by an instantaneous over pressure such as by an impact or nuclear explosion type event.

Minute amounts of stishovite has been found within diamonds.[41]

Cristobalites[edit | edit source]

Cristobalite spheres appear within obsidian. Credit: Rob Lavinsky.

Def. a high-temperature (above 1470°C) polymorph of α-quartz with cubic, Fd3m, space group no. 227, and a tetragonal form (P41212, space group no. 92) is called cristobalite.

Sodalites[edit | edit source]

A sample of sodalite-carbonate pegmatite from Bolivia has a polished rock surface. Credit: .

Sodalite is a rich royal blue mineral massive sodalite samples are opaque, crystals are usually transparent to translucent. Occurring typically in massive form, sodalite is found as vein fillings in plutonic igneous rocks such as nepheline syenites.

Lazurites[edit | edit source]

Lazurite is a deep blue tectosilicate. Credit: .

Lazurite is a tectosilicate mineral with sulfate, sulfur and chloride with formula: (Na,Ca)8[(S,Cl,SO4,OH)2|(Al6Si6O24)]. It is a feldspathoid and a member of the sodalite group. The colour is due to the presence of S3- anions. Lazurite is a product of contact metamorphism of limestone.

Glaucophanes[edit | edit source]

This is a specimen of glaucophane with fuchsite. Credit: .

Often a mineral appears blue due to the presence of copper or sulfur. Glaucophane is a blue silicate that owes its color to its characteristic formation.

Glaucophane is a mineral belonging to the amphibole group, chemical formula Na2Mg3Al2Si8O22(OH)2. The blue color is very diagnostic for this species. It, along with the closely related mineral riebeckite are the only common amphibole minerals that are typically blue. Glaucophane forms in metamorphic rocks that are either particularly rich in sodium or that have experienced low temperature-high pressure metamorphism such as would occur along a subduction zone. This material has undergone intense pressure and moderate heat as it was subducted downward toward the mantle. It is glaucophane's color that gives the blueschist facies its name. Glaucophane is also found in eclogites that have undergone retrograde metamorphism.[42]

Hauynes[edit | edit source]

This is a specimen of Haüyne on augite from the Somma-Vesuvius Complex, Naples Province, Italy. Credit: .

Hauyne, haüyne or hauynite occurs in Vesuvian lavas in Monte Somma, Italy.[43] It is a tectosilicate mineral with sulfate, with endmember formula Na3Ca(Si3Al3)O12(SO4).[44] It is a feldspathoid and a member of the sodalite group.[45][46] Haüyne occurs in phonolites and related leucite- or nepheline-rich, silica-poor, igneous rocks; less commonly in nepheline-free extrusives[47][45][46][48] and metamorphic rocks (marble).[45]

Olivines[edit | edit source]

This image is a visual close up of green sand which is actually olivine crystals that have been eroded from lava rocks. Credit: Brocken Inaglory.
This is a visual image of a forsterite crystal. Credit: Azuncha.

Def. "[a]ny of a group of olive green magnesium-iron" orthosilicates "that crystallize in the orthorhombic system"[49] is called an olivine.

At right is a visual close up of green sand which is actually olivine crystals that have been eroded from lava rocks. Some olivine crystals are still inside the lava rock.

Forsterite (Mg2SiO4) is the magnesium rich end-member of the olivine solid solution series.

Forsterite is associated with igneous and metamorphic rocks and has also been found in meteorites. In 2005 it was also found in cometary dust returned by the Stardust probe.[50] In 2011 it was observed as tiny crystals in the dusty clouds of gas around a forming star.[51]

Two polymorphs of forsterite are known: wadsleyite (also orthorhombic) and ringwoodite (isometric). Both are mainly known from meteorites.

Chlorites[edit | edit source]

The name greenstone comes from the green hue imparted by the colour of the metamorphic minerals within the mafic rocks. Chlorite, actinolite and other green amphiboles are the typical green minerals.

Pyroxenes[edit | edit source]

This very rare, sharp, complete-all-around pyroxene is circa mid to late 1800s. Credit: Robert Lavinsky.

Def. a group of monoclinic or orthorhombic, single chain inosilicates with the general formula of X Y(Si,Al)2O6, where

X is calcium, sodium, ferrous iron (Fe2+), magnesium, zinc, manganese and lithium;
Y is chromium, aluminum, ferric iron (Fe3+), magnesium, manganese, scandium, titanium, vanadium, and ferrous iron (Fe2+)

is called a pyroxene.

The pyroxenes are a group of important rock-forming inosilicate minerals found in many igneous and metamorphic rocks. They share a common structure consisting of single chains of silica tetrahedra and they crystallize in the monoclinic and orthorhombic systems. Pyroxenes have the general formula XY(Si,Al)2O6 (where X represents calcium, sodium, iron+2 and magnesium and more rarely zinc, manganese and lithium and Y represents ions of smaller size, such as chromium, aluminium, iron+3, magnesium, manganese, scandium, titanium, vanadium and even iron+2). Although aluminium substitutes extensively for silicon in silicates such as feldspars and amphiboles, the substitution occurs only to a limited extent in most pyroxenes.

At right is an image of a very rare, sharp, complete-all-around pyroxene is from Ducktown District, Polk County, Tennessee, USA, circa mid to late 1800s.

Amphiboles[edit | edit source]

Def. a group of monoclinic or orthorhombic double chain inosilicates with the general formula of

X2Y5Z8O22(OH)2 where
X is magnesium, ferrous iron (Fe2+), calcium, lithium, sodium, and ferric iron (Fe3+)
Y is Al, Mg, or Fe or less commonly Mn, Cr, Ti, Li, etc.
Z is chiefly Si or Al

is called an amphibole.

Micas[edit | edit source]

Here is mica in a rock. Credit: Rpervinking.

Def. a group of monoclinic phyllosilicates with the general formula[52]

in which X is K, Na, or Ca or less commonly Ba, Rb, or Cs;
Y is Al, Mg, or Fe or less commonly Mn, Cr, Ti, Li, etc.;
Z is chiefly Si or Al, but also may include Fe3+ or Ti;
dioctahedral (Y = 4) and trioctahedral (Y = 6)

is called a mica.

Feldspars[edit | edit source]

Def. "[a]ny of a large group of ... aluminum [tectosilicates] of the alkali metals sodium, potassium, calcium and barium"[53] is called feldspar.

Plagioclases[edit | edit source]

Def. "[a]ny of a group of aluminum silicate feldspathic minerals ranging in their ratio of calcium to sodium"[54] is called plagioclase.

Alkali metals[edit | edit source]

This is a sodium chloride crystal of the mineral halite. Credit: United States Geological Survey and the Mineral Information Institute.

The alkalis, or alkali metals, are the group 1 elements of the Periodic Table. In addition to the true metals: lithium (Li), sodium (Na), potassium (K), rubidium (Rb), caesium (Cs), and francium (Fr), hydrogen (H) is usually included.

Each of the elements in group 1 has or may have native mineral occurrences on Earth or elsewhere nearby.

Halite (NaCl) is probably the most common mineral containing sodium at 50 at %. It is a cubic mineral usually found in arid locations on Earth. Occurrences have clear, white, purple, blue, yellow, orange, and red varieties.[26]

Oxidanes[edit | edit source]

On April 13, 2004, a blanket of hail fell during a storm in Cerro El Pital, El Salvador. Credit: Wanakoo.

Oxidane minerals contain more than 25 at or molecular % H2O.

The most common oxidane on the surface of the Earth is the liquid known as water. It occurs in the atmosphere as water vapor, and as a mineral usually referred to as ice.

Ices[edit | edit source]

This is a very large hailstone from the NOAA Photo Library. Credit: NOAA Legacy Photo; OAR/ERL/Wave Propagation Laboratory.

A megacryometeor is a very large chunk of ice sometimes called huge hailstones, but do not need to form in thunderstorms.

A megacryometeor is a very large chunk of ice which, despite sharing many textural, hydro-chemical and isotopic features detected in large hailstones, is formed under unusual atmospheric conditions which clearly differ from those of the cumulonimbus cloud scenario (i.e. clear-sky conditions). They are sometimes called huge hailstones, but do not need to form in thunderstorms. Jesus Martinez-Frias, a planetary geologist at the Center for Astrobiology in Madrid, pioneered research into megacryometeors in January 2000 after ice chunks weighing up to 6.6 pounds (3.0 kg) rained on Spain out of cloudless skies for ten days.

Def. "pieces of ice falling as precipitation"[55] are called hail.

Def. "[a] single ball of hail"[56] is called a hailstone.

Def. water ice crystals falling as light white flakes are called snow.

Blue ices[edit | edit source]

This image shows the blue water ice, or blue ice, of a glacier. Credit: .

Blue ice occurs when snow falls on a glacier, is compressed, and becomes part of a glacier Blue ice was observed in Tasman Glacier, New Zealand in January 2011.[57] Ice is blue for the same reason water is blue: it is a result of an overtone of an oxygen-hydrogen (O-H) bond stretch in water which absorbs light at the red end of the visible spectrum.[58]

Alkaline earth metals[edit | edit source]

This shows a relatively large, apparently single crystal of bromellite. Credit: Kjell Gatedal.

Bromellite is BeO, with 50 at % beryllium.[26]

Aluminides[edit | edit source]

Near the top center of this image is a gray reflective flake of native aluminum. Credit: Vasil Arnaudov.

The aluminides are those naturally occurring minerals with a high atomic % aluminum.

In the image on the right of a flake of native aluminum, the scale bar = 1 mm.

Aluminum is the third most abundant element (after oxygen and silicon) in the Earth's crust, and the most abundant metal there. It makes up about 8% by mass of the crust, though it is less common in the mantle below.

Carbonides[edit | edit source]

Natural, or native element, piece of graphite has been cut from a larger piece. Credit: USGS.

Carbonides are naturally occurring minerals composed of 50 atomic percent, or more, carbon. Carbonide-like minerals with greater than 25 at % carbon are also included. This separates carbon containing minerals from carbonates which are at most 25 at % carbon.

Diamonds[edit | edit source]

This image shows a diamond already removed from its natural location in a rock. Credit: Eurico Zimbres FGEL/UERJ.

Def. "[a] naturally occurring, glimmering glass-like allotrope of carbon in which each atom is surrounded by four others in the form of a tetrahedron"[59] is called a diamond.

Carpathites[edit | edit source]

Radial spray of highly lustrous, canary-yellow carpathite lathes reach to 2.0 cm. Credit: Rob Lavinsky.
This is carpathite under ultraviolet light. Credit: Rama.

Def. a solid, homogeneous, monoclinic (space group P2/c, no. 13, or P21/c, no. 14), naturally occurring, chemical compound with the formula C24H12 that results from natural inorganic processes is called a carpathite.

Carpathite (aka Karpatite) is a very rare organic species (C24H12).[26] It is a polycyclic aromatic hydrocarbon (PAH). This specimen is from the old Picacho Mercury Mine of California. It exhibits a radial spray of highly lustrous, canary-yellow carpathite lathes to 2.0 cm on drusy quartz. Another crossed cluster of crystals above reach 3.0 cm. It has 66.7 at % carbon.

Pnictogens[edit | edit source]

Arsenopyrite is an arsenic-containing mineral. Credit: jjharrison89.

Def. any "element from group 15 of the periodic table; nitrogen, phosphorus, arsenic, antimony and bismuth"[60] is called a pnictogen.

Some of the pnictogens like phosphorus, arsenic, antimony and bismuth, occur as metalloids.

Arsenopyrite on the right is 33.3 at % arsenic.

Apatites[edit | edit source]

This fluorapatite specimen is primarily violet. Credit: Vassil.
The color of the purple apatites (which are to almost 1 cm in size) leaps out at you. Credit: Rob Lavinsky.

Fluorapatite a sample of which is shown at right is a mineral with the formula Ca5(PO4)3F (calcium fluorophosphate). Fluorapatite as a mineral is the most common phosphate mineral. It occurs widely as an accessory mineral in igneous rocks and in calcium rich metamorphic rocks. It commonly occurs as a detrital or diagenic mineral in sedimentary rocks and is an essential component of phosphorite ore deposits. It occurs as a residual mineral in lateritic soils.[61]

At left is another fluorapatite example that is violet in color on quartz crystals.

Chalcogens[edit | edit source]

The image shows native sulfur, yellow, and calcite crystals, clear or white. Credit: Didier Descouens.

The chalcogens are the elements of group 16 of the Periodic Table. These include oxygen (O), sulfur (S), selenium (Se), tellurium (Te), polonium (Po), and livermorium (Lv).

Chalcogen minerals are more than 25 at % chalcogens.

Hibonites[edit | edit source]

An example of common occurring brownish hibonite. Credit: Kelly Nash.
This specimen from Madagascar has a bluish cast that may indicate a composition similar to those grains found in meteorites. Credit: Rock Currier.

Usually, Hibonite ((Ca,Ce)(Al,Ti,Mg)12O19) as shown at right is a brownish black mineral. It is rare, but is found in high-grade metamorphic rocks on Madagascar. Some presolar grains in primitive meteorites consist of hibonite. Hibonite also is a common mineral in the Ca-Al-rich inclusions (CAIs) found in some chondritic meteorites. Hibonite is closely related to hibonite-Fe (IMA 2009-027, ((Fe,Mg)Al12O19)) an alteration mineral from the Allende meteorite.[62] Hibonite is blue perhaps like the image at left in meteorite occurrence.

Carbonates[edit | edit source]

Large crystal of Calcite is on display. Credit: Alkivar, National Museum of Natural History.

Carbonates have more than 25 at or molecular % CO3.

Calcite has the chemical formula CaCO3.[26]

Calcite contains one oxide: CO3, or carbonate. It is 50 molecular % carbonate and 50 at % calcium.

Malachites[edit | edit source]

Malachite is a mineral occurring on Earth, like many greens, is colored by the presence of copper, specifically by basic copper(II) carbonate.[63] Credit: Rob Lavinsky.

Malachite is a mineral that occurs in rocks at or near the interface between Earth's atmosphere and crust.

Halogens[edit | edit source]

The fluorite crystal is just over 1 cm and is rimmed on one side with sparkling pyrite. Credit: Robert Lavinsky.

Halogens are elements in column 7A of the periodic table. They occur as a principal component in a variety of minerals.

On the right, is an example of almost completely clear fluorite (CaF2).

Impurities can give color. Some halogen minerals are called halides.

Metalloids[edit | edit source]

This massive native arsenic with quartz and calcite is from Ste. Marie-aux-mines, Alsace, France. Credit: Aram Dulyan.

Metalloids are elements whose properties are intermediate between metals and solid nonmetals or semiconductors.

A variety of elements are often considered metalloids:

  1. boron, considered here in the boronides,
  2. aluminum, a face-centered cubic metal, considered in the aluminides,
  3. silicon, here in the siliconides,
  4. gallium (it can occur in the liquid state as a mineraloid),
  5. germanium,
  6. arsenic,
  7. selenium, also included in the chalcogens,
  8. indium,
  9. tin,
  10. antimony,
  11. tellurium, also included in the chalcogens,
  12. polonium, considered as among the heavy metals and
  13. astatine, here is with the halogens.

Metals[edit | edit source]

These specimens are some of the most easily recognizable, dramatic and highly sought after silver specimens from the Western Hemisphere. Credit: Robert Lavinsky.

Metals constitute a large portion of the Periodic Table of elements. Their combinations with each other and the other elements result in the minerals that compose rocky-objects.

Generally, the transition metals constitute the periodic table of elements from groups 3-12, beginning with scandium (Sc) and ending with element number 112 Copernicium.

Usually, these and the other metals are divided into several subgroups for specific purposes:

  1. Metalloids - gallium (Ga) through selenium (Se) and cadmium (Cd) through tellurium (Te).
  2. Alkaline earth metals - group 2: beryllium (Be) through radium (Ra).
  3. Alkali metals - group 1: lithium (Li) through francium (Fr).
  4. Body-centered cubic metals - titanium (Ti) through chromium (Cr), zirconium (Zr) through molybdenum (Mo), and hafnium (Hf) through tungsten (W).
  5. Heavy metals - mercury (Hg) through polonium (Po).
  6. Lanthanides - lanthanum (La) through lutetium (Lu), also called the rare-earths.
  7. Precious metals - ruthenium (Ru) through silver (Ag) and rhenium (Re) through gold (Au).
  8. Siliconides.
  9. Transition metals are often restricted to manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), and zinc (Zn).
  10. Transuranics - neptunium (Np) through Roentgenium (Rg) and Copernicium (Cn).

The category of metals also includes aluminum, scandium (Sc), yttrium (Y), technetium (Tc), and the actinides.

Body-centered cubic metals[edit | edit source]

A face-centered cubic close-packed unit cell structure is outlined in red. Credit: Owen Graham.
This is a stick and ball model of a fcc unit cell. Credit: Baszoetekouw.
These models compare a fcc unit cell with hexagonal close-packing (hcp). Credit: Twisp.
This is a native chromium nugget. Credit: Neal Ekengren.

Metals in general fall into two groups of close-packing structures: face-centered cubic (fcc) and hexagonal close-packed (hcp). These two are the most efficient way to pack a bunch of hard marbles into the smallest space.

An fcc structure differs from a hcp in the number of distinct close-packed layers: hcp has two, symbolized with A below B, and fcc which has three with A below B, but C above B before A again.

Native chromium such as the nugget in the image on the right is very rare. It is also a hard mineral, probably because of an oxide coating giving it a slight bluish cast.

Precious metals[edit | edit source]

This very elaborate, 3-dimensional cluster of gold shows complex and minute crystallization patterns, and is overall hackly in texture. Credit: Robert Lavinsky.

Precious metals are usually rare, chemically relatively inert, and often colorful.

They are transition metals ruthenium (Ru) through silver (Ag) and rhenium (Re) through gold (Au).

Transition metals[edit | edit source]

An uncommon slabbed and polished specimen of lustrous, metallic, elemental native iron in basalt from Germany. Credit: Robert Lavinsky.

Usually, these and the other metals are divided into several subgroups for specific purposes:

  1. Actinides - group 3: actinium (Ac) through lawrencium (Lr).
  2. Alkali metals - group 1: lithium (Li) through francium (Fr).
  3. Alkaline earth metals - group 2: beryllium (Be) through radium (Ra).
  4. Aluminides - aluminum (Al): native aluminum and minerals above 25 at % Al.
  5. Body-centered cubic metals - titanium (Ti) through chromium (Cr), zirconium (Zr) through molybdenum (Mo), and hafnium (Hf) through tungsten (W).
  6. Heavy metals - mercury (Hg) through polonium (Po), copernicium (Cn) through livermorium (Lv).
  7. Lanthanides - lanthanum (La) through lutetium (Lu), also called the rare-earths.
  8. Metalloids - gallium (Ga) through selenium (Se) and cadmium (Cd) through tellurium (Te).
  9. Precious metals - technetium (Tc) through silver (Ag) and rhenium (Re) through gold (Au).
  10. Rare earth metals group 3: scandium (Sc), yttrium (Y), the Lanthanides, and the Actinides.
  11. Siliconides - native silicon and minerals above 25 at % Si.
  12. Transition metals are often restricted to manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), and zinc (Zn), but generally include Sc through zinc (Zn), Y through cadmium (Cd), lanthanum through mercury, actinium through copernicium (Cn).
  13. Transuranics - neptunium (Np) through roentgenium (Rg) and copernicium (Cn).

For this lecture, the transition metals are limited to those minerals containing significant quantities of manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), and zinc (Zn).

Generally, a mineral is a transition metal mineral if it is more than 25 at % transition metals.

Kamacites[edit | edit source]

Kamacite, Nantan (Nandan) iron meteorites, Nandan County, Guangxi Zhuang Autonomous Region, China. Size: 4.8×3.0×2.8 cm. The Nantan irons, a witnessed fall in 1516, have a composition of 92.35% iron and 6.96% nickel. Credit: .

Kamacite is an alloy of iron and nickel, which is only found on earth in meteorites. The proportion iron:nickel is between 90:10 to 95:5; small quantities of other elements, such as cobalt or carbon may also be present. The mineral has a metallic luster, is gray and has no clear cleavage although the structure is isometric-hexoctahedral. Its density is around 8 g/cm³ and its hardness is 4 on the Mohs scale. It is also sometimes called balkeneisen.

Taenites[edit | edit source]

Taenite (Fe,Ni) is a mineral found naturally on Earth mostly in iron meteorites. It is an alloy of iron and nickel, with[nickel proportions of 20% up to 65%. ... Taenite is one of four known Fe-Ni meteorite minerals: The others are kamacite, tetrataenite, and antitaenite. ... It is opaque with a metallic grayish to white color. The structure is isometric-hexoctahedral. Its density is around 8 g/cm³ and hardness is 5 to 5.5 on the Mohs scale. Taenite is magnetic. The crystal lattice has the c≈a= 3.582ű0.002Å.[64] The Strunz classification is I/A.08-20, while the Dana classification is . It is a Hexoctahedral (cubic) in structure.

Tetrataenites[edit | edit source]

Tetrataenite is a native metal found in meteorites with the composition FeNi. It is one of the mineral phases found in meteoric iron.[65][66][67]

Antitaenites[edit | edit source]

Antitaenite is a meteoritic metal alloy mineral composed of iron and nickel, 20-40% Ni (and traces of other elements) that has a face centered cubic crystal structure. ... [It exists] as a new mineral species occurring in both iron meteorites and in chondrites[68] ... The pair of minerals antitaenite and taenite constitute the first example in nature of two minerals that have the same crystal structure (face centered cubic) and can have the same chemical composition (same proportions of Fe and Ni) - but differ in their electronic structures: taenite has a high magnetic moment whereas antitaenite has a low magnetic moment.[69] [This difference] arises from a high-magnetic-moment to low-magnetic-moment transition occurring in the Fe-Ni bi-metallic alloy series.[70]

Covellites[edit | edit source]

This covellite specimen is from the Black Forest of Germany. Credit: .

Covellite has been found in veins at depths of 1,150 meters, as the primary mineral. Covellite formed as clusters in these veins reaching one meter across.

Heavy metals[edit | edit source]

This is a cadmium-containing mineral cadmoindite. Credit: David Hospital.

Def. any "metal that has a specific gravity greater than about 5"[71] is called a heavy metal.

Heavy metals usually includes cadmium, indium, tin, antimony, mercury, thallium, lead, and bismuth.

Heavy metals are mercury (Hg) through polonium (Po), copernicium (Cn) through livermorium (Lv).

The cadmoindite specimen on the right has about 28.6 at % cadmium.

Breithauptites[edit | edit source]

This is a specimen of Breithauptite on calcite from the Samson Mine, St Andreasberg, Harz Mountains, Lower Saxony, Germany. Credit: Leon Hupperichs.

Breithauptite is a nickel antimonide mineral with the simple formula NiSb. Breithauptite is a metallic opaque copper-red mineral crystallizing in the hexagonal - dihexagonal dipyramidal crystal system. It is typically massive to reniform in habit, but is observed as tabular crystals. It has a Mohs hardness of 3.5 to 4 and a specific gravity of 8.23.

It occurs in hydrothermal calcite veins associated with cobalt–nickel–silver ores.

Cinnabars[edit | edit source]

Cinnabar is a naturally occurring cochineal-red, towards brownish red and lead-gray, mercury-sulfide mineral. Credit: H. Zell.

Cinnabar or cinnabarite (red mercury(II) sulfide (HgS), native vermilion), is the common ore of mercury. Its color is cochineal-red, towards brownish red and lead-gray. Cinnabar may be found in a massive, granular or earthy form and is bright scarlet to brick-red in color.[72] Generally cinnabar occurs as a vein-filling mineral associated with recent volcanic activity and alkaline hot springs. Cinnabar is deposited by epithermal ascending aqueous solutions (those near surface and not too hot) far removed from their igneous source.

Crocoites[edit | edit source]

This Crocoite specimen is from the Red Lead Mine, Tasmania, Australia. Credit: .
A sample of crocoite crystals from Dundas extended mine in Tasmania and is used to make the first synthetic orange pigment, chrome orange. Credit: .

Crocoite is a mineral consisting of lead chromate, PbCrO4. Crystals are of a bright hyacinth-red color. Relative rarity of crocoite is connected with specific conditions required for its formation: an oxidation zone of lead ore bed and presence of ultramafic rocks serving as the source of chromium (in chromite).

The second crocoite on the right from Dundas extended mine in Tasmania is used to make the first synthetic orange pigment, chrome orange.

Native indiums[edit | edit source]

"Indium minerals are very rare ; only 7 species have been defined so far : roquesite, CuInS2 (Picot & Pierrot, 1963) ; indite, FeIn2S4, and dzhalindite, In(OH)3 (Genkin & Murav'eva, 1963) ; sakuraiite, (Cu,Fe,Zn)3(In,Sn)S4 (Kato, 1965) ; native indium (Ivanov, 1966b) ; yixunite, PtIn (Yu Tsu-Hsiang et al., 1976) ; petrukite, (Cu,Fe,Zn,Ag)3(Sn,In)S4 (Kissin & Owens, 1989)."[73]

Rare earths[edit | edit source]

This is a specimen of gadolinite. Credit: WesternDevil.

Def. "naturally occurring oxides of the lanthanide metals"[74] are called rare earths.

Gadolinite on the right often contains a variety of rare earth elements.

Actinides[edit | edit source]

Actinide minerals, or actinides, are those with unusually high concentrations, atomic per cents, or weight per cents, of the actinide elements.

Autunites[edit | edit source]

This gamma-ray spectrum contains the typical isotopes of the uranium-radium decay line. Credit: Wusel007.

Elements usually emit a gamma-ray during nuclear decay or fission. The gamma-ray spectrum at right shows typical peaks for 226Ra, 214Pb, and 214Bi. These isotopes are part of the uranium-radium decay line. As 238U is an alpha-ray emitter, it is not shown. The peak at 40 keV is not from the mineral. From the color of the rock shown the yellowish mineral is likely to be autunite.

Autunite occurs as an oxidizing product of uranium minerals in granite pegmatites and hydrothermal deposits.

Pitchblendes[edit | edit source]

This is an image of the mineral pitchblende, or uraninite. Credit: Geomartin.
These crystals are uraninite from Trebilcock Pit, Topsham, Maine. Credit: Robert Lavinsky.

Uraninite is a radioactive, uranium-rich mineral and ore with a chemical composition that is largely UO2, but also contains UO3 and oxides of lead, thorium, and rare earth elements. It is most commonly known as pitchblende (from pitch, because of its black color. All uraninite minerals contain a small amount of radium as a radioactive decay product of uranium. Uraninite also always contains small amounts of the lead isotopes 206Pb and 207Pb, the end products of the decay series of the uranium isotopes 238U and 235U respectively. The extremely rare element technetium can be found in uraninite in very small quantities (about 0.2 ng/kg), produced by the spontaneous fission of uranium-238.

The image at left shows well-formed crystals of uraninite. The image at right shows botryoidal unraninite. Because of the uranium decay products, both sources are gamma-ray emitters.

Thorianites[edit | edit source]

This specimen of thorianite is from th Ambatofotsy pegmatite in Madagascar. Credit: Robert Lavinsky.

Thorianite is a rare thorium oxide mineral, ThO2.[75] ... [It has a] high percentage of thorium; it also contains the oxides of uranium, lanthanum, cerium, praseodymium and neodymium. The mineral is slightly less radioactive than pitchblende, but is harder to shield due to its high energy gamma rays. It is common in the alluvial gem-gravels of Sri Lanka, where it occurs mostly as water worn, small, heavy, black, cubic crystals.

Torbernites[edit | edit source]

Torbernitte is a hydrated green copper uranyl phosphate mineral. Credit: Didier Descouens.

Torbernite is a radioactive, hydrated green copper uranyl phosphate mineral, found in granites and other uranium-bearing deposits as a secondary mineral. Torbernite is isostructural with the related uranium mineral, autunite. The chemical formula of torbenite is similar to that of autunite in which a Cu2+ cation replaces a Ca2+. The number of water hydration molecules can vary between 12 and 8, giving rise to the variety of metatorbernite when torbernite spontaneously dehydrates.

Uranophanes[edit | edit source]

Uranophane is a calcium uranium silicate hydrate mineral. Credit: United States Geological Survey.

Uranophane Ca(UO2)2(SiO3OH)2·5H2O is a rare calcium uranium [nesosilicate] hydrate mineral that forms from the oxidation of uranium bearing minerals. Uranophane is also known as uranotile. It has a yellow color and is radioactive.

Transuranics[edit | edit source]

This mineral, Aeschynite, probably contains on the order of a few atoms of neptunium at any one time, as part of the complex decay chain of the uranium that makes up a much larger fraction of the sample. Credit: Theodore Gray.

Minerals containing transuranics are not rare. But, the stability of such isotopes makes it unlikely to find large concentrations of specific elements.

The transuranics start after uranium (U) in the periodic table. They include the named elements: plutonium (Pu), americium (Am), curium (Cm), berkelium (Bk), californium (Cf), einsteinium (Es), fermium (Fm), mendelevium (Md), nobelium (No), lawrencium (Lr), rutherfordium (Rf), dubnium (Db), seaborgium (Sg), bohrium (Bh), hassium (Hs), meitnerium (Mt), darmstadtium (Ds), roentgenium (Rg), copernicium (Cn), flerovium (Fl), and livermorium (Lv).

Mineraloids[edit | edit source]

This is a specimen of obsidian from Lake County, Oregon. Credit: Locutus Borg.

Def. a "substance that resembles a mineral but does not exhibit crystallinity"[76] is called a mineraloid.

Def. a "chemical element existing in an uncombined state in nature"[26] is called a native element.

Def. a naturally occurring, silvery-colored, metallic liquid, composed primarily of the chemical element mercury, is called mercury, or native mercury.

Def. "[a] hard, generally yellow to brown translucent fossil resin"[77] is called an amber.

Def. "[a] flammable liquid ranging in color from clear to very dark brown and black, consisting mainly of hydrocarbons"[78] is called petroleum.

Def. a naturally occurring black glass is called an obsidian. An example is in the image on the right.

Def. "[a] small, round, dark glassy object, composed of silicates"[79] is called a tektite.

Def. a naturally occurring, hydrous, amorphous form of silica, where 3% to 21% of the total weight is water is called an opal.

Moldavites[edit | edit source]

This image shows Moldavite from Besednice, Bohemia. Credit: H. Raab (Vesta).

Moldavite is an olive-green or dull greenish vitreous substance possibly formed by a meteorite impact. It is one kind of tektite.

"Because of their difficult fusibility, extremely low water content, and its chemical composition, the current overwhelming consensus among Earth scientists is that moldavites were formed 15 million years ago during the impact of a giant meteorite in present-day Nördlinger Ries. Splatters of material that was melted by the impact cooled while they were actually airborne and most fell in central Bohemia—traversed by [the] Vltava river ... Currently, moldavites have been found in [an] area that includes southern Bohemia, western Moravia, the Cheb Basin (northwest Bohemia), Lusatia (Germany), and Waldviertel (Austria).[80] Isotope analysis of samples of moldavites have shown a beryllium-10 isotope composition similar to the composition of Australasian tektites (Australites)and Ivory Coast tektites (Ivorites). Their similarity in beryllium-10 isotope composition indicates that moldavites, Australites, and Ivorites consist of near surface and loosely consolidated terrestrial sediments melted by hypervelocity impacts.[81]

Mineral astronomy[edit | edit source]

In this image the mineral panguite occurs with the scandium-rich silicate davisite embedded in a piece of the Allende meteorite. Credit: Caltech/Chi Ma.

Mineral astronomy is the use of various astronomical techniques to locate and identify minerals and mineral deposits, especially on astronomical rocky objects.

At right is a thin-section image of a slice through the Allende meteorite. The Allende meteorite "lit up Mexico's skies in 1969 [and] scattered thousands of meteorite bits across the northern Mexico state of Chihuahua. ... Panguite [a titanium dioxide mineral] is believed to be among the oldest minerals in the solar system, which is [estimated to be] about 4.5 billion years old. Panguite belongs to a class of refractory minerals that could have formed only under the extreme temperatures and conditions present in the infant solar system."[82]

Explorations[edit | edit source]

Airborne gamma-ray spectrometry is now the accepted leading technique for uranium prospecting with worldwide applications for geological mapping, mineral exploration & environmental monitoring.

Moon[edit | edit source]

These images show a very young lunar crater on the side of the moon that faces away from Earth. Credit: ISRO/NASA/JPL-Caltech/USGS/Brown Univ.
This image of Earth's moon is a three-colour composite of reflected near-infrared radiation from the Sun. Credit: ISRO/NASA/JPL-Caltech/Brown Univ./USGS.

"These images show a very young lunar crater on the side of the moon that faces away from Earth, as viewed by NASA's Moon Mineralogy Mapper [M3] on the Indian Space Research Organization's Chandrayaan-1 spacecraft. On the left is an image showing brightness at shorter infrared wavelengths. On the right, the distribution of water-rich minerals (light blue) is shown around a small crater. Both water- and hydroxyl-rich materials were found to be associated with material ejected from the crater."[83]

"NASA's Moon Mineralogy Mapper, an instrument on the Indian Space Research Organization's Chandrayaan-1 mission, took [the image at right] of Earth's moon. It is a three-colour composite of reflected near-infrared radiation from the sun, and illustrates the extent to which different materials are mapped across the side of the moon that faces Earth. Small amounts of water were detected on the surface of the moon at various locations. This image illustrates their distribution at high latitudes toward the poles. Blue shows the signature of water, green shows the brightness of the surface as measured by reflected infra-red radiation from the sun and red shows a mineral called pyroxene."[84]

Europa[edit | edit source]

Frozen sulfuric acid on Jupiter's moon Europa is depicted in this image produced from data gathered by NASA's Galileo spacecraft. Credit: NASA/JPL.

"Frozen sulfuric acid on Jupiter's moon Europa is depicted in this image produced from data gathered by NASA's Galileo spacecraft. The brightest areas, where the yellow is most intense, represent regions of high frozen sulfuric acid concentration. Sulfuric acid is found in battery acid and in Earth's acid rain."[85]

"This image is based on data gathered by Galileo's near infrared mapping spectrometer."[85]

"Europa's leading hemisphere is toward the bottom right, and there are enhanced concentrations of sulfuric acid in the trailing side of Europa (the upper left side of the image). This is the face of Europa that is struck by sulfur ions coming from Jupiter's innermost moon, Io. The long, narrow features that crisscross Europa also show sulfuric acid that may be from sulfurous material extruded in cracks."[85]

The darker regions are areas where Europa's primarily water ice surface has a higher mineral content.

Enceladus[edit | edit source]

The image at the left was taken in visible green light. The image at the right has been color-coded to make faint signals in the plume more apparent. Credit: NASA.

At right is a pair of images showing "[a] fine spray of small, icy particles emanating from the warm, geologically unique province surrounding the south pole of Saturn’s moon Enceladus[. It] was observed in a Cassini narrow-angle camera image of the crescent moon taken on Jan. 16, 2005. Taken from a high-phase angle of 148 degrees -- a viewing geometry in which small particles become much easier to see -- the plume of material becomes more apparent in images processed to enhance faint signals [right image of the pair]."[86]

"Though the measurements of particle abundance are more certain within 100 kilometers (60 miles) of the surface, the values measured there are roughly consistent with the abundance of water ice particles measured by other Cassini instruments (reported in September, 2005) at altitudes as high as 400 kilometers (250 miles) above the surface."[86]

"The image at the left was taken in visible green light. A dark mask was applied to the moon's bright limb in order to make the plume feature easier to see."[86]

"The image at the right has been color-coded to make faint signals in the plume more apparent. Images of other satellites (such as Tethys and Mimas) taken in the last 10 months from similar lighting and viewing geometries, and with identical camera parameters as this one, were closely examined to demonstrate that the plume towering above Enceladus' south pole is real and not a camera artifact. The images were acquired at a distance of about 209,400 kilometers (130,100 miles) from Enceladus. Image scale is about 1 kilometer (0.6 mile) per pixel."[86]

Neptune[edit | edit source]

In these Hubble images of Neptune the clouds are tinted pink because they are reflecting near-infrared light. Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA).

The set of four images at right are taken with the Hubble Space Telescope on June 25-26, 2011, just before Neptune arrived at the same location in space where it was discovered nearly 165 (Earth) years before (i.e. 1 Neptunian year on July 11, 2011).

"The snapshots were taken at roughly four-hour intervals [of a 16 h rotation period], offering a full view of the planet. The images reveal high-altitude clouds in the northern and southern hemispheres. The clouds are composed of methane ice crystals."[87]

"The snapshots show that Neptune has more clouds than a few years ago, when most of the clouds were in the southern hemisphere. These Hubble views reveal that the cloud activity is shifting to the northern hemisphere. It is early summer in the southern hemisphere and winter in the northern hemisphere."[87]

"The clouds are tinted pink because they are reflecting near-infrared light."[87]

Hypotheses[edit | edit source]

  1. High-temperature, high-pressure minerals exist in the core of the Earth.
  2. High-temperature, high-pressure minerals can be produced through natural electrochemistry.

See also[edit | edit source]

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