2Chromium and PGM (Platinum Group Metals) Mantle like material intrudes into continental crustReacts with sulfides and metals settle out at bottomCommon way to make Nickel Sulfide DepositsChromium and PGMs tend to settle out in specific layersGet a little from the Sudberry meteor impact too.
4The Ocean Floor Mechanism Ocean floor comes from mantle like material forming new crust at a spreading ocean plate boundarySometimes when continents collide or run into things just right a chunk of sea floor gets dragged up into a continentCalled an Ophiolite sequenceBottom part of the ocean floor can contains pods of Chromium rich ore
6Where Chromium and PGMs are Found Green colored areasAt plate edges areScooped up oceanFloor withChromium podsBlack areas showWhere chromiumAnd PGM layersSettled from mantleIntrusions intoContinental crustYou can get a few placers from these primary deposits too.
7Main Ore Mineral of Chromium is Chromite Chromite (black) interlayered withSepentine (greenish)Fresh Chromite SurfaceFe2+Cr2O4 46% ChromiumS.G – 5.1Hardness 5.5Color Black to Brownish blackTends to have granular textureWeatheredChromite Surface
8Platinum, Osmium, Rhodium, Ruthenium, Palladium = PGMs Native PlatinumNative PalladiumPGMs can be native metals or substituted into other minerals
9Sperrylite PtAs2 57% Platinum S.G. 10.5 Hardness 6-7 Metal to white and brittle
10Podform Chromite Deposits are Smaller 22,000 tons of ore is a median – big ones may be 250,000 tonsGrade of the ore is around 46% Chromic Oxide
12Little Chromite Pods May be Only 143 tons Ore grades are again around 46% Chromic oxide
13Chromium Processing Chromite tends to be lumpy big chunks Allows some separation in miningRest if needed can usually be done with gravity separationJigsHeavy media separatorsTablesLump Ore is Then Sent to Smelter FurnacesOften melted together with ironSome very intensive oxygen and ammonia processes may kill off residual carbon.
14The Gravity Concentrators Use the fact that something is heavyHeavies have more momentum –Shaking TablesHeavies sink faster – JigLight stuff floats in a heavy fluid – Heavy Media Separator
15PGMs – A Tough Act to Process PGMs in a good case are associated with nickel and copper sulfidesIn nasty cases some of them are trapped in gangue mineralsTry to Float out the PGMsThen send them to the smelter
16What Do We Use Them ForChromium is mostly as a stainless steel alloy with some chemical and plating usesPGMs are used mostly for catalysts for air pollution control systems, with some laboratory applications, and some jewlery
17What is Chromium Worth?About $0.40 to $0.60/lb (prices based on chrome content of ferro-chrome
18What Are PGMs WorthAbout $5,000 to $10,000 per lb but varies with metalPlatinum around $12,000, Palladium around $4,500Rhodium around $12,000 to $48,000