Geochemically Scarce metals

 

For information and statistics on many metallic and non-metallic resources, check out the mineral commodity summaries on the US Geological Survey web site at http://minerals.usgs.gov/minerals/pubs/mcs  

 

 

 

Precious   metals

 

 

 

Gold (Au)

 

 

Properties and use

 

Attractive color, dense, very ductile, inert, good conductor of electricity.   Jewelry, ornaments, electronics, gold leaf

 

Measures in troy ounces (1/12th pound  = 31.1grams)

Alloys with platinum (white gold), silver (electrum), copper (red gold), mercury (amalgam)

 

Main use, however,  is as a monetary metal. Gold coins.   Gold standard (abolished 1931)

Price fixed at $35/oz from 1934 to 1968 to stabilize currencies (countries currency was valued related to how much gold they had in storage);  however lessened price of gold.

Price peaked in 1980 at $850/oz

 

 

Ore deposits and mining

 

Primary deposits are hydrothermal (occurs with copper and silver) veins or disseminated– native metal  or combined with silver and/or copper;  often produced as a byproduct of copper mining.

 

Placer deposits because dense and inert. Witwatersrand, S. Africa a major deposit is a paleo-placer deposit (conglomerate) – mined to depths of 3.5 km (12,000 ft)

 

 

 

Processing

Easy to smelt, or may be extracted using cyanide solution in heap leaching

 

 

Production and producers

 

More than 60 countries producing, but dominated by seven: S. Africa, US (mainly Nevada), Australia, China, Canada, Russia, Peru

 

 

 

SILVER  (Ag)

 

Properties and use

Pleasing appearance, malleable and ductile, best  conductor of electricity of all metals (25% silver) . Jewelry, electronics

 

Halide compounds (ie compounds with bromine,chlorine, iodine) have photochemical properties – used in conventional photography.

 

Monetary metal  -in coins;  wide usage by Romans; a synonym for money.  Silver coins from mines in Joachimsthal (Joachim’s valley) in what is now Czech Republic wildly used as currency in Middle ages. These became known as Joachimsthalers, or “thalers” leading to the modern word “dollar”.

 

 

Ore deposits and mining

 

Hydrothermal:  Native silver, argentite (sulfide), tetrahedrite.  Like gold often a byproduct of copper mining.

 

 

 

Processing

 

Easy to smelt

 

 

 

Production and producers

 

Many countries, but no single dominant one Mexico, Peru, US, Canada and Chile produce 60% of world production.

 

Recently consumption of silver has exceeded production.  May change as digital photography takes hold.

 

 

 

 

 

 

 

PLATINUM (Pt) and Platinum Group (Palladium, Rhodium, Iridium, Ruthenium and Osmium)

(occur in same geologic setting)

 

Properties and use

Silvery, malleable, inert, high melting temperature.  Chemical catalyst. Used in Catalytic converters. Laboratory equipment.

 

Ore deposits and mining

Native metals, sufides and arsenides.    Magmatic segregating deposits – Bushveld complex, S. Africa.  Often associated with chromite. 

 

Also in placers (dense, inert) – Ural mountain deposits

 

 

Processing

Native element so easy to process

 

 

Production and producers

 

South Africa and Russia dominate.  US production from the Stillwater Complex, Montana