Minerals/Blues

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

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.

Colors[edit | edit source]

Main article: Radiation astronomy/Colors
This is a cross section of HSL color space. Credit: 8 leaf-clover.{{free media}}

Each form of radiation that an astronomical entity can emit, absorb, fluoresce, transmit, or reflect has a spectrum in time, space, intensity, or variation.

A spectrum of variation shows its colors.

Alloy minerals[edit | edit source]

"Grain size varies from 98 to 530 lm with an average of *150 lm. Minor [elements] oxidation [from an iron–nickel–chromium–cobalt–phosphorus alloy] is evidenced by the presence of a light brown and blue surface layer composed of very fine-grained (<1 lm) crystals on the surface."[1] "[T]he oxidation of minor elements in metallic alloys in the early solar system" is indicated to possess at instances a blue surface layer.[1]

Oxidanes[edit | edit source]

Main article: Geominerals/Oxidanes
This image shows the blue water ice, or blue ice, of a glacier. Credit: McKay Savage from London, UK.{{free media}}

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.[2] 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.[3]

Covellites[edit | edit source]

This covellite specimen is from the Black Forest of Germany. Credit: Ra'ike.{{free media}}

Covellite [CuS] 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. Covellite is a hexagonal form of CuS.[4] Covellite is a chalcogen.

Fluorites[edit | edit source]

Fluorescing fluorite is from Boltsburn Mine Weardale, North Pennines, County Durham, England, UK. Credit: Didier Descouens.

Many samples of fluorite exhibit fluorescence under ultraviolet light, a property that takes its name from fluorite.[5] Many minerals, as well as other substances, fluoresce. Fluorescence involves the elevation of electron energy levels by quanta of ultraviolet light, followed by the progressive falling back of the electrons into their previous energy state, releasing quanta of visible light in the process. In fluorite, the visible light emitted is most commonly blue, but red, purple, yellow, green and white also occur. The fluorescence of fluorite may be due to mineral impurities such as yttrium, ytterbium, or organic matter in the crystal lattice. In particular, the blue fluorescence seen in fluorites from certain parts of Great Britain responsible for the naming of the phenomenon of fluorescence itself, has been attributed to the presence of inclusions of divalent europium in the crystal.[6]

Calcites[edit | edit source]

Calcite fluoresces blue under short wave ultraviolet light. Credit: Herbert Art Gallery and Museum, Coventry.{{free media}}
Natural radiation interacts with sheared calcite to produce blue colors. Credit: Stephanie Clifford.{{free media}}

Between 190 and 1700 nm, the ordinary refractive index varies roughly between 1.9 and 1.5, while the extraordinary refractive index varies between 1.6 and 1.4.[7]

On the right is blue calcite produced by natural irradiation.

Hauynes[edit | edit source]

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

Hauyne, haüyne or hauynite occurs in Vesuvian lavas in Monte Somma, Italy.[8] It is a tectosilicate mineral with sulfate, with endmember formula Na3Ca(Si3Al3)O12(SO4).[9] It is a feldspathoid and a member of the sodalite group.[10][11] Haüyne occurs in phonolites and related leucite- or nepheline-rich, silica-poor, igneous rocks; less commonly in nepheline-free extrusives[12][10][11][13] and metamorphic rocks (marble).[10]

Haüyne, or haüynite, is cubic, a member of the sodalite group, and has the formula (Na,Ca)4-8Al6Si6O24(SO4)1-2.[4]

Sodalites[edit | edit source]

These are a stereo pair that can be seen in stereo by those who can cross their eyes slightly. Credit: John Alan Elson.

"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."[14]

"The following features and examples imply why stress of tectosilicate lattices can be linked to the luminescence emission at 340 nm: (i) natural metastable hatch-cross texture in exsolved Na/K microcline at 300 K, (ii) radiation damaged areas in natural quartz, (iii) natural quartz with large amounts of silicon substitution with aluminum and alkali ions, (iv) artificial porous silica with OH groups adsorbed to the surfaces, (v) sodalite feldspathoid in which many tetrahedral silicon Si4+ are substituted with intrinsic aluminum–chlorine defects, (vi) [ionoluminescence] IL at low temperature of all tectosilicate analyzed samples enhanced the 340 nm peak."[15]

Sodalite has the formula Na4Al3Si3O12Cl.[4]

Lazurites[edit | edit source]

Lazurite is a deep blue tectosilicate. Credit: Didier Descouens.

"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".[16]

Lazurite (Lapis Lazuli) has the formula (Na,Ca)8(Al,Si)12O24(S,So4).[4]

Glaucophanes[edit | edit source]

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

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.[17]

Glaucophane is an amphibole that has the formula Na2(Mg,Fe2+)3Al2Si8O22(OH)2.[4]

Hibonites[edit | edit source]

This specimen from Madagascar has a bluish cast that may indicate a composition similar to those grains found in meteorites. Credit: Rock Currier.
Blue hibonite occurs in an inclusion in the Murray meteorite. Credit: George R. Rossman.

Usually, "Hibonite ((Ca,Ce)(Al,Ti,Mg)12O19) 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 [chondrite] chondritic meteorites. Hibonite is closely related to hibonite-Fe (IMA 2009-027, ((Fe,Mg)Al12O19)) an alteration mineral from the Allende meteorite.[18] [Hibonite] is blue [perhaps like the image at left] in meteorite occurrence."[19]

"Ti3+ - Ti4+ interactions are found in meteoritic minerals. A example of the blue color caused in some minerals by this interaction is the color of the fine-grained, titanium-containing, calcium aluminum oxide mineral, hibonite, in an inclusion known as the Blue Angel in the Murchison metorite. This mineral absorbs red light but lets blue light pass. The optical spectrum of this mineral has a band with a maximum absorption hear 690 nm. Better examples include blue hibonite in the Murray meteorite [image on the right] and the hibonite-bearing inclusions in the Vigarano CV3 chondrite meteorite."[20]

Spertiniites[edit | edit source]

The image shows light blue spertiniite from the Dzhezkazgan Mine in Kazakhstan. Credit: Leon Hupperichs.

Spertiniite has the chemical formula Cu(OH)2.

Calumetites[edit | edit source]

This specimen of calumetite is from the Akmeek No. 2 Mine in Keweenaw County, Michigan, held at the A. E. Seaman Mineral Museum. Credit: Chris857.{{free media}}

Calumetite has the chemical formula Cu(OH,Cl)2·2H2O.[4]

Lavendulans[edit | edit source]

Lavendulan is a relatively rare arsenate and the intense blue color is very distinctive. Credit: Rob Lavinsky.

Lavendulan has the chemical formula (Ca,Na)2Cu5(AsO4)4Cl·4-5H2O.[4]

Zoisites[edit | edit source]

In 1967, a purple-blue variety of zoisite, named tanzanite after its country of discovery, was found near the slopes of Mount Kilimanjaro on the border of Tanzania and Kenya. Credit: The University of Arizona Mineral Museum.

Tanzanite, a variety of zoisite that is purple-blue member of the epidote group.[4]

Zoisite has the chemical formula Ca2Al3Si3O12OH.[4]

Linarites[edit | edit source]

This specimen of a copper mineral called linarite contains unusual large crystals. Credit: Wynne Parry.

Linarite is an monoclinic azure blue mineral with the chemical formula of PbCuSO4(OH)2.[4]

Spinels[edit | edit source]

In tetrahedral sites, Co2+ causes a blue color found in some spinels from Baffin Island. Credit: George R. Rossman.

On the right are some blue spinels from Baffin Island. Usually, spinel has the formula MgAl2O4. When Co2+ substitutes for Mg2+, the spinel (or cobalt spinel) is blue. In the formula this would be (Mg,Co)Al2O4.

Aquamarines[edit | edit source]

Here is a blue aquamarine from the Tenente Ananias area, Rio Grande do Norte, Brazil. Credit: George R. Rossman.

On the right is a blue aquamarine (a variety of beryl) from the Tenente Ananias area, Rio Grande do Norte, Brazil.

Halites[edit | edit source]

Blue halite from Germany is the result of exposure to natural radiation. Credit: George R. Rossman.

"Blue halite from Germany is the result of exposure to natural radiation. Initially, if halite (common salt) is exposed to gamma radiation, it turns amber because of F-centers. They are mostly electrons trapped at sites of missing Cl- ions. In time the electrons migrate to Na+ ions and reduce it to Na metal. Atoms of Na metal, in turn, migrate to form colloidal sized aggregrates of sodium metal. They are the cause of the blue color."[21]

Hypotheses[edit | edit source]

Main article: Hypotheses
  1. The origins of blue color in minerals may be as varied as the formation conditions of the minerals themselves.

See also[edit | edit source]

References[edit | edit source]

  1. ↑ 1.0 1.1 Dante S. Lauretta; Britney E. Schmidt (April 1, 2009). "Oxidation of Minor Elements from an Iron–Nickel–Chromium–Cobalt–Phosphorus Alloy in 17.3% CO2–H2 gas mixtures at 700–1000 °C". Oxidation of Metals 71 (3-4): 219-35. doi:10.1007/s11085-009-9140-7. http://link.springer.com/article/10.1007/s11085-009-9140-7. Retrieved 2013-06-01. 
  2. ↑ Harvey, Eveline (14 January 2011). "NZ blue ice sighting an unexpected treat for tourists". The New Zealand Herald. Retrieved 21 September 2011.
  3. ↑ Why Is Water Blue
  4. ↑ 4.00 4.01 4.02 4.03 4.04 4.05 4.06 4.07 4.08 4.09 Willard Lincoln Roberts; George Robert Rapp Jr.; Julius Weber (1974). Encyclopedia of Minerals. New York, New York, USA: Van Nostrand Reinhold Company. pp. 121-2. ISBN 0-442-26820-3. 
  5. ↑ Stokes, G. G. (1852). "On the Change of Refrangibility of Light". Philosophical Transactions of the Royal Society of London 142: 463–562. doi:10.1098/rstl.1852.0022. 
  6. ↑ K. Przibram (1935). "Fluorescence of Fluorite and the Bivalent Europium Ion". Nature 135 (3403): 100. doi:10.1038/135100a0. 
  7. ↑ D.W. Thompson (1998). "Determination of optical anisotropy in calcite from ultraviolet to mid-infrared by generalized ellipsometry". Thin Solid Films 313–4 (1-2): 341–6. doi:10.1016/S0040-6090(97)00843-2. 
  8. ↑ Farndon and Parker (2009). Minerals, Rocks and Fossils of the World. Lorenz Books
  9. ↑ http://rruff.info/ima
  10. ↑ 10.0 10.1 10.2 Gaines (1997). Dana’s New Mineralogy Eighth Edition. New York: Wiley. 
  11. ↑ 11.0 11.1 "Hauyne". Mindat.org. Retrieved 11 August 2011.
  12. ↑ "Hauyne". Webminerals. Retrieved 11 August 2011.
  13. ↑ Handbook of Mineralogy
  14. ↑ "Sodalite". San Francisco, California: Wikimedia Foundation, Inc. February 25, 2013. Retrieved 2013-05-28.
  15. ↑ J. Garcia-Guineaa; V. Correcher; L. Sanchez-Muñoz; A.A. Finch; D.E. Hole; P.D. Townsend (21 September 2007). "On the luminescence emission band at 340 nm of stressed tectosilicate lattices". Nuclear Instruments and Methods in Physics Research A 580 (1): 648-51. http://www.researchgate.net/profile/V_Correcher/publication/245121262_On_the_luminescence_emission_band_at_340_nm_of_stressed_tectosilicate_lattices/links/54ca04bb0cf2807dcc287c60.pdf. Retrieved 2015-09-06. 
  16. ↑ "Lazurite, In: Wikipedia". San Francisco, California: Wikimedia Foundation, Inc. April 21, 2013. Retrieved 2013-05-28.
  17. ↑ http://rruff.geo.arizona.edu/doclib/hom/glaucophane.pdf Handbook of Mineralogy
  18. ↑ IMA Mineral List with Database of Mineral Properties
  19. ↑ "Hibonite". San Francisco, California: Wikimedia Foundation, Inc. March 7, 2013. Retrieved 2013-06-01.
  20. ↑ George R. Rossman (16 June 2009). "Colors in minerals caused by Intervalence Charge Transfer (IVCT)". Pasadena, California USA: California Institute of Technology. Retrieved 2015-10-29.
  21. ↑ George R. Rossman (12 April 2013). "Colors from ionizing radiation". Pasadena, California USA: California Institute of Technology. Retrieved 2015-10-29.

External links[edit | edit source]

{{Radiation astronomy resources}}

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