Minerals/Metals/Precious

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).

Golds

Main articles: Minerals/Golds and Golds

This gold nugget (placer gold) is 9.5 mm across at its widest. Credit: James St. John.

Gold (Au) is the most prestigious metal known, but it's not the most valuable. Gold is the only metal that has a deep, rich, metallic yellow color. Almost all other metals are silvery-colored. Gold is very rare in crustal rocks - it averages about 5 ppb (parts per billion). Where gold has been concentrated, it occurs as wires, dendritic crystals, twisted sheets, octahedral crystals, and variably-shaped nuggets. It most commonly occurs in hydrothermal quartz veins, disseminated in some contact- & hydrothermal-metamorphic rocks, and in placer deposits. Placers are concentrations of heavy minerals in stream gravels or in cracks on bedrock-floored streams. Gold has a high specific gravity (about 19), so it easily accumulates in placer deposits. Its high density allows prospectors to readily collect placer gold by panning.

Platinums

Main articles: Minerals/Platinums and Platinums

This is a native platinum nugget, locality Kondyor mine, Khabarovsk Krai, Russia. Credit: Alchemist-hp.

Platinum can also occur as nuggets such as the one imaged on the right from Russia.

Silvers

Main articles: Minerals/Silvers and Silvers

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

Native silver is on calcite from Kongsberg, Norway. Credit: Aram Dulyan.

Native silver does occur as cubic, octahedral, or dodecahedral crystals; "also elongated, arborescent, reticulated, or as thin to thick wires."

Iridiums

The image is of a cubic crystal of native iridium. Credit: Norman King.

Native iridium such as the small cubic crystal shown in the image on the right is rare.

Osmiums

Main articles: Minerals/Osmiums and Osmiums

A crystal of native osmium from Nishni Tagil, Ural, Russia, is shown. Credit: Thomas Witzke.

The crystal of native osmium shown on the right is about 2 mm across.

Palladiums

Main articles: Minerals/Palladiums and Palladiums

This is a palladium nugget. Credit: Hudson Institute of Mineralogy.

This piece of native palladium is from the Mednorudyanskoye Cu Deposit, Nizhnii Tagil, Sverdlovskaya Oblast', Middle Urals, Urals Region, Russia. Credit: Hudson Institute of Mineralogy.

"Natural Palladium [like the nugget shown on the right] always contains some Platinum."

This palladium nugget is from Bom Sucesso Creek, Serro, Minas Gerais, Brazil.

"(Pd,Cu) alloys, some with the approximate composition PdCu₄, are reported by Kapsiotis et al. (2010)."

The piece of native palladium [image on the left] from the Mednorudyanskoye Cu Deposit, Nizhnii Tagil, Sverdlovskaya Oblast', Middle Urals, Urals Region, Russia, probably contains some copper.

Potarites

This piece of potarite is from Serro, Minas Gerais, Brazil. Credit: Hudson Institute of Mineralogy.

Potarite has the chemical formula PdHg.

On the right is a piece of potarite is from Serro, Minas Gerais, Brazil.

Rheniums

Main articles: Minerals/Rheniums and Rheniums

This is an image of the first find of native rhenium in the transitional clay layer at the Cretaceous/Paleogene boundary in the Gams Section. Credit: A. F. Grachev, S. E. Borisovsky, and A. V. Grigor’eva.

"Native rhenium was first discovered in the Earth's crust in wolframites from a rare metal deposit in the Transbaikal region [1]. [...] The study of the lunar regolith from two sites revealed native rhenium particles with different morphological features: irregular dense particles from Mare Fecunditatis and spheroidal particles from Mare Crisium. The origin of particles (less than 10 µm in size) is assigned to exhalative processes [2]. Among the extraterrestrial objects, native rhenium was found in Ni-iron and silicates from the Allende meteorite [3]."

Rhodiums

Main articles: Minerals/Rhodiums and Rhodiums

This image of microbreccia contains rhodium-bearing ferroplatinum. Credit: T. A. Gornostaeva, P. M. Kartashov, A. V. Mokhov, and O. A. Bogatikov.

The image on the right contains small particles of native rhodium-bearing ferroplatinum. This sample was obtained from the lunar regolith "by the Luna-16 automatic station".

"Terrestrial iron-free rhodium-bearing platinum with the composition of Pt_0.68Rh_0.32 in association with platinum-bearing rhodium Rh_0.57Pt_0.43 [...] was originally discovered in heavy fractions from basic rocks (norite, gabbro, and anorthosite) in the upper zone of the layered Stillwater intrusion (Montana, United States) [2]."

Rutheniums

Main articles: Minerals/Rutheniums and Rutheniums

This is a piece of native ruthenium from Verkhneivinsk, Neiva river, Sverdlovskaya Oblast', Middle Urals, Urals Region, Russia. Credit: Hudson Institute of Mineralogy.

The piece of native ruthenium in the image on the right contains some iridium. It is from Verkhneivinsk, Neiva river, Sverdlovskaya Oblast', Middle Urals, Urals Region, Russia.

Hypotheses

Main article: Hypotheses

1. Precious metals have variable value so may only be used as an interim investment.

See also

• Transition metals