The Weathering Product Minerals ©2010 Dr. B. C. Paul Credit is given particularly to the following sources, USGS, Mapofworld.com,

Weathering Can Enrich Minerals of Interest by Removing Other Stuff Minerals that weather well may form Placer nuggets –Gold –Cassiterite (Tin) –Zircon –Illmenite –Rutile –Diamonds Often mixed with sand since quartz also weathers very well

Tropical Weathering Can Leave an Entire Mass of Depleted Soil and Rock Called Laterites –Need very wet cycle –Good draining and a dry cycle –Nice warm temperatures Wet cycle leaches and soluabilizes ions Dry cycle brings them to the surface Next wet cycle can wash them away Need to have low erosion or everything can get washed away – plains in stable continents in tropical areas are favorable Leaves silica, iron, alumina behind A lot formed in the Mesozoic Era – was a major drop in world temp about 65 million years ago that we have never recovered from

Alumina Precipitates as Gibbsite Al(OH) 3, Diaspore AlO(OH), Boehemite AlO(OH) – Mix often known as Bauxite –Enriched in aluminum hydroxides –Becomes an ore of Aluminum

Major Bauxite Deposits

More Bauxite Deposits

Grade Tonnage Relationship for Deposits Over 28 Million tons above 45% Al 2 O 3

Bauxite Production and Reserves Production in Millions Of Tons Reserves in units of 50 Million Tons Reserve Base Is Huge!

Mining Bauxite Because they tend to be weathered layers on flat lying low erosion topography they are usually strip mined

Processing Bauxite Often begin with screening -Some of the silica is in -The form of fines that can be -Separated from the courser -Alumina minerals

Next to Pressurized Alkali Digestion Raise the temperature to 450 F and 500 Psi The dissolve with sodium hydroxide (lye) pH 14

Use Counter Current Decantation through thickeners to remove iron mud Fresh wash water Dirtiest Solution

Filter Remaining fine silicate particles are Filtered out with vacuum filter presses

Cooled in Crystalization Tank A white powder of Al 2 O 3 and AlOH is produced The precipitate is collected by filtration.

Calcined in a Rotary Kiln at 800F to convert everything to Aluminum Oxide

Aluminum Smelting Aluminum Oxide is mixed with cryolite flux to lower the melting temperature. A molten bath is prepared. A carbon electrode is lowered – Carbon combines with oxygen and leaves aluminum Hall Heroult Process

What is Aluminum Used For?

What is Aluminum Worth? Aluminum is worth around $1/lb

What Happens When A Mantle Melt Intrusion is Tropically Weathered? Garnierite – a mixture of Ni bearing layered magnesium silicates Produced by weathering of Serpentine and Dunite

Nickel Laterites Have 3 Times the Reserves in Traditional Sulfides

Distribution of Resources

Grade Tonnage Relations Around 1.5 to 3% With about 330,000,000 tons

Importance of Laterites is Increasing

Processing of Nickel Laterites Most currently done by Pyrometallurgy Dry and Calcine in a Rotary Kiln Smelt in an Electric Furnace with Carbon to take away the Oxygen and leave metal