The Vein Things of the World ©2010 Dr B. C. Paul Materials in these slides have been organized by the author but many of the facts and images are taken from other sources.

Vein Minerals Fractures and voids in rock masses are available to be filled in by something else Often water solutions will precipitate minerals to fill those voids Solutions commonly come from 3 places –Water percolating down from the surface –Water forced out of volcanic magma –Water forced out of rocks that are under great heat and pressure

Where Solutions Get Their Minerals They can leach them out of the rocks around them They can pick them up from the molten rock mass they come from They can pick them up from rock that is being metamorphosed

The Hydrothermal Driver Solutions normally pick up minerals when they are hot and then deposit them in vein fillings as they cool down Example – The Carlin Trend Gold Deposits of Nevada (about 8% of world gold production) –Water percolated down from the surface –Mantle convection was trying to rip North America apart under Nevada so the crust was thinning and the Mantle heat was near the surface –The water heated up – dissolved gold out of granetic rock masses and then deposited dispersed veinlets of gold.

More Drivers The Rand in South Africa (about 40% of Worlds Gold Reserves) –About 3 billion years ago before continents were well developed mantle intrusives rich in gold spewed out in lava flows –These mantle lava flows became elevated around a basin (the Rand) Erosion weathered away other rock and left placer deposits of gold in the basin. –The gold placers became trapped in new rock deposits that were metamorphosed

Gold Gold tends not to react well with other elements –Thus it is very common as native gold Native gold metal is usually always loaded up with something else –Silver will almost always be present, but other things can be there too. Gold does form minerals with Tellurium so you do get Gold Telluride minerals

Native Gold Load in Quartz Placer Nuggets Electrum (Gold/Silver) Au Hardness Density 15 to depending on purity

Calaverite AuTe % Gold Color Yellow to Yellowish White Hardness 2.5 S.G Non Fluorescent Non Magentic

Krennerite AuTe % Gold Color White to Blackish Yellow Hardness 2.5 S.G Non Fluorescent Non Magnetic

Sylvanite (Au,Ag) 2 Te % Gold Color Yellowish silver white to white Hardness S.G Non Fluorescent Magnetic after heating

Petzite Ag 3 AuTe % Gold 41.7% Silver Color Iron Black to Steel Gray Hardness 2.5 S.G Non Fluorescent Non Magnetic

Native Silver Ag Color Silver White, Gray White, Gray Hardness S.G Non Fluorescent Non Magnetic

Chlorargyrite AgCl 75.3% Silver Color Purplish Gray, Green, White, Colorless Hardness S.G Non Fluorescent Non Magnetic

Argentite Ag 2 S 87.1% Silver Color Black to Lead Gray Hardness S.G. 7.3 Non Fluorescent Non Magnetic

Acanthite Ag 2 S 87.1% Silver (Low Temperature crystal structure Argentite is high temp structure) Color Lead Gray, Gray, Iron Black Hardness S.G. 7.3 Non Fluorescent Non Magnetic

Proustite Ag 3 AsS % Silver Color Blood Red, Redish gray Hardness S.G Non Fluorescent Non Magnetic

Hessite Ag2Te 62.8% Silver Color Lead Gray, Steel Gray Hardness S.G Non Fluorescent Non Magnetic

Gold Uses

Processing Gold How coarse is the gold? (and is it in a native state) –Grind the ore –Use shaking tables or gravity concentrators to get coarse “free milling gold” If gold is fine an old method is mercury amalgamation –Gold and mercury form a heavy complex that settles to the bottom of the reaction vessel –Heating will drive off the mercury and leave the gold –Mercury water pollution makes method unacceptable in many areas for large scale work.

Method of Choice is Cyanide Leach Solution Ground Ore Heap Leach

Boosting Solution Concentration (If Needed) Carbon will adsorb gold from cyanide solutions Can back flush the columns with strong alkali to release the gold back to high Grade solutions

Merrill Crowe Process Solutions are clarified (crud settled or filtered out). Zinc is added under vacuum And the gold precipitates out.

Overcoming Challenges Other minerals or Gold in Telluride –Boost cyanide strength –Roast the ore to destroy interfering sulfides The Preg Robbing Problem –Carbon in the ore will adsorb the gold back if you leach it Roast the ore to destroy the carbon – hope you have plenty of money Bubble through Chlorine to destroy the carbon

Carbon in Pulp – Carbon in Leach Load it with your own activated carbon and suck up the gold right out of the Leach with your own better carbon.

Gold Production and Reserves

What is Gold Worth? About $5000 to $15000 a pound

Silver Uses

Production and Reserves

What is Silver Worth? About $100 to $250 per pound

Tellurium Uses A metal alloy to increase machinability without changing electrical resistance –Reduces metal fatigue problems Biggest use is in chemicals and catalysts –Vulcanizing, rubber, synthetic fibers Electronics and imaging devices Cadmium and Tellurium based solar cells may be a coming breakthrough technology –Not a fact yet

Tellurium Processing and Reserves When copper is electrorefined elements left behind in the “slimes” –Selenium –Tellurium They are byproducts

Tellurium Recovery Electrowinning of copper leaves solid residues at the bottom of cells (Copper Anode Slimes) The Slimes are Sulfuric Acid Leached –Dissolves residual copper and tellurium Iron is added to precipitate copper and tellurium Precipitate is leached with caustic soda –Dissolves out the Tellurium

Tellurium Recovery Continued Acid is then used to neutralize the caustic solution –Tellurium precipitates as Tellurus Acid Re-dissolve the Tellurus Acid with Caustic Soda –Put it in a electrowinning cell and electrowin Tellurium

What is Tellurium Worth? About $40 to $60 per pound

Arsenic Uses About 50% is used as a wood preserving agent – use is declining due to public fear A hardening agent in metal alloys Added to lead shot Pure forms used in gallium arsenide for computer chips and electronics

Arsenopyrite Massive Crystalline FeAsS 46% arsenic Color Tin white, light steel gray Hardness 5 S.G Non Fluorescent Magnetic after heating

Orpiment As2S3 60.9% Arsenic Color Lemon Yellow, Brownish Yellow, Orangish Yellow Hardness S.G Non Fluorescent Non Magnetic

Realgar AsS 70% Arsenic Color Auro Red Dark Red, Orange Yellow Hardness S.G Non Fluorescent Non Magnetic

Sources of Arsenic Usually a coproduct or byproduct Can roast arsenopyrite for direct production Copper often comes with arsenic minerals Arsenic minerals are markers found with Gold Actual arsenic production may follow more where production takes place than original source

What is Arsenic Worth Around 50 cents a pound

Mercury Uses

Cinnabar HgS 86.2% Mercury Color Red, Brownish Pink, Brown, can be gray Hardness S.G. 8.1 Non Fluorescent Non Magnetic

Processing of Mercury Cinnabar will sweat mercury and break down on heating Is a lot of byproduct recovery from gold operations

Production and Reserves of Mercury US actually has byproduct production and is considered to have a surplus of Mercury from recycle.

What is Mercury Worth? About $3 to $10 per pound

Antimony Uses

Stibnite Sb 2 S % Antimony Color Gray, Bluish Gray, Black Hardness 2 S.G Non Fluorescent Non Magnetic

Tennantite (Cu,Fe) 12 As 4 S % Arsenic, 47.51% Copper Color Steel Gray, Black Hardness S.G Non Fluorescent Non Magnetic

Production and Reserves of Antimony

What is Antimony Worth About $1 to $3 per pound

Fluorspar Uses

Fluorite CaF2 48.7% Fluorine Color White, Yellow, Green, Red, Blue Hardness 4 S.G Fluorescent Non Magnetic

Processing Fluorite Fluorspar can be a direct fluxing agent as a mineral in its own right –Recovered by grinding and floatation –Trick is that there are usually things like Galena, Sphalerite, and Barite with it Have to float these sulfides out first Then have to float fluorspar in heated floation cells If acid HF is to be produced for chemicals the Fluorite is treated with sulfuric acid in a reactor

World Production and Reserves

What is Fluorspar Worth? Around 10 to 15 cents Per Pound