# Minerals/Metals/Precious

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

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

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

## Silvers

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

## Iridiums

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

## Osmiums

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

## Palladiums

"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 PdCu$_4$, 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

Potarite has the chemical formula PdHg.
On the right is a piece of potarite is from Serro, Minas Gerais, Brazil.

## Rheniums

"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."

## Rhodiums

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$_{0.68}$Rh$_{0.32}$ in association with platinum-bearing rhodium Rh$_{0.57}$Pt$_{0.43}$ [...] 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

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

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