chromium and platinum group metals ©2009 dr. b. c. paul acknowledgement is given to ,...
TRANSCRIPT
Chromium and Platinum Group Metals
©2009 Dr. B. C. Paul
Acknowledgement is given to www.d.umn.edu, webmineral.com, geology.com, brittanica.com, webmineral.com, geology.about.com, periodictable.com,
mindat.org, johnbetts-fineminerals.com, USGS Bull 1693, earthsci.org, SME
Mineral Processing Handbook, icdachromium.com
Chromium and PGM (Platinum Group Metals)
• Mantle like material intrudes into continental crust– Reacts with sulfides and metals settle out at
bottom– Common way to make Nickel Sulfide Deposits
• Chromium and PGMs tend to settle out in specific layers
• Get a little from the Sudberry meteor impact too.
Settled Chromium Deposits
The Ocean Floor Mechanism
• Ocean floor comes from mantle like material forming new crust at a spreading ocean plate boundary
• Sometimes when continents collide or run into things just right a chunk of sea floor gets dragged up into a continent– Called an Ophiolite sequence– Bottom part of the ocean floor can contains
pods of Chromium rich ore
Chromium Pods in an Ocean Floor Sequence
Where Chromium and PGMs are Found
Green colored areasAt plate edges areScooped up oceanFloor withChromium pods
Black areas showWhere chromiumAnd PGM layersSettled from mantleIntrusions intoContinental crust
You can get a few placers from these primary deposits too.
Main Ore Mineral of Chromium is Chromite
Chromite (black) interlayered withSepentine (greenish)
Fresh Chromite Surface
WeatheredChromite Surface
Fe2+Cr2O4 46% ChromiumS.G. 4.5 – 5.1Hardness 5.5Color Black to Brownish blackTends to have granular texture
Platinum, Osmium, Rhodium, Ruthenium, Palladium = PGMs
Native Platinum
Native Palladium
PGMs can be native metals or substituted into other minerals
Sperrylite
PtAs2 57% PlatinumS.G. 10.5Hardness 6-7Metal to white and brittle
Podform 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
PGMs may be in the parts per billion range
Little Chromite Pods May be Only 143 tons
Ore grades are again around 46% Chromic oxide
Chromium Processing
• Chromite tends to be lumpy big chunks– Allows some separation in mining– Rest if needed can usually be done with gravity
separation• Jigs• Heavy media separators• Tables
• Lump Ore is Then Sent to Smelter Furnaces– Often melted together with iron– Some very intensive oxygen and ammonia processes
may kill off residual carbon.
The Gravity Concentrators
Use the fact that something is heavy
Heavies have more momentum –Shaking Tables
Heavies sink faster – Jig
Light stuff floats in a heavy fluid – Heavy Media Separator
PGMs – A Tough Act to Process
• PGMs in a good case are associated with nickel and copper sulfides– In nasty cases some of them are trapped in
gangue minerals
• Try to Float out the PGMs
• Then send them to the smelter
What Do We Use Them For
• Chromium is mostly as a stainless steel alloy with some chemical and plating uses
• PGMs are used mostly for catalysts for air pollution control systems, with some laboratory applications, and some jewlery
What is Chromium Worth?
Chromium Price/lb in $2009 to 2007
0
0.2
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0.6
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1900
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$200
9/lb
$2009/lb
About $0.40 to $0.60/lb (prices based on chrome content of ferro-chrome
What Are PGMs Worth
PGMs Price in $2009 to 2007
0
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$200
9/lb
$2009/lb
About $5,000 to $10,000 per lb but varies with metalPlatinum around $12,000, Palladium around $4,500Rhodium around $12,000 to $48,000
Production and Reserves of Chromium
Chromium Production and Reserves
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Prod*20 reserves metrictonnes
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es Other
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Kazakhastan
India
U.S
PGMs Production and ReservesProduction and Reserves of PGMs
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Prod*20 Reserves
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Zimbabwe
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Russia
Columbia
Canada
US