non-metallic resources: diamondsresources.seattlecentral.edu/faculty/kgagnon/env170/diamonds...

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Non-metallic Resources:Diamonds

Rock cycle and plate boundaries• One or more minerals held together by a matrix

Rock types: Igneous• Form from the solidification and crystallization of

-magma (molten rock below ground)-lava (molten rock above ground)

• Most common examples-Basalt-Granite

http://csmres.jmu.edu/geollab/fichter/IgnRx/Introigrx.html

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Rock types: Igneous• Four types of igneous rocks


Bowen’sreactionseries:

arranged bytemperatureof formation

Mafic mineralsContain iron and magnesium

Felsic mineralsNo iron and magnesium

Rock types: Igneous• Classified by texture and color/composition

“slow” = thousands to millions of years“fast” = days to weeks

Any aphanitic rock with theword “porphyry”

Two stage cooling; one slowunderground creating visiblephenocrysts, the second fast atthe earth's surface producing afine grained groundmass.

Porphyritic (two grain sizes)

Granite, diorite, gabbroVery slow cooling; crystalsgrow to visible size.

Phaneritic (coarse grained)

Rhyolite, andesite, basaltSlow cooling; microscopiccrystal growth.

Aphanitic (fine grained)

Pumice, scoriaVery fast cooling with rapidgas escape forming bubbles inthe non-crystalline rock.

Vesicular

ObisdianVery fast (hours) cooling; non-crystalline.

GlassyExamplesCooling HistoryTexture


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Pegmatite

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Rock types: Igneous rock distribution


Rock types: Igneous rock distribution


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Composition: Carbon CarbonHardness: Hardest known, 10 1.0Electrically: Insulator ConductorLuster: High, dispersion of light Dull, metallicUses: Gemstone, cutting Pencils, lubricant

Diamond Graphite

Carbon allotropes

http://www.chem.ufl.edu/~itl/2041_u01/lectures/lec_h.html

Diamond formation: Primary depositsKimberlite rock

- Volatile rich (CO2 & H2O) ultramafic rock- [Rarely] contains xenoliths (solid rocks incorporated intomagma) of diamond

http://www.diamond-all.com/Diamond.html

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Diamond formation• Originate in Earth’s mantle, 150 km deep (~90 miles)

http://dao.mit.edu/8.231/carbon_phase_diagram.jpg

Diamond formation: Primary depositsDiatreme- Explosive volcanic pathway

to Earth’s mantle- 50 m high tuff ring- Youngest event ~50 million

years ago

- 1 in 200 contain diamonds

http://www.diamond-all.com/Diamond.html

Diamond formation: Primary deposits

http://www.brc-diamondcore.com/s/Technical.asp?ReportID=282496

Kimberlite pipe Lamproite pipe(Older than 2.5 Byr) (Youngest 50,000 years)

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Diamond formation: Primary deposits• Kimberley mine

-Dug without any machinery, 1871-1908-460 m diameter by 1100 m deep-3 tons of diamonds were extracted

South Africa

Diamond formation: Primary deposits• Open pit mine

-Used when material is too loose for underground tunnels-Explosives break up layers of “overburden”-Rocks removed and inspected-Overburden replaced or made into a landfill

Canada


Siberia

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South Africa


Australia (Lamproite pipe, broader cone)


Canada

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Diamond formation: Primary deposits• Hydraulic mining

-Jets of water loosen gem material-Sluices catch gravel slurry for inspection-Ended in 1960’s

Diamond formation: Primary deposits• Strip mining

-Similar to open pit mines but done in long strips-Strip one material is removed-Strip two material fills strip one . . .

http://apod.nasa.gov/apod/ap061122.html

Bucket wheelexcavator: moves

material 100 m by 25m deep per day

Diamond formation: Primary deposits• Underground mining

http://www.diavik.ca/ENG/ouroperations/1624_underground_mining_equipment.asp

Diavik open pit mine,Northwest Territories Canada

55 million year old pipe

Planned 2012 transition to anunderground mine

Red: three kimberlite pipesGreen/blue: planned mine

network

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Diamond formation: Primary deposits• Underground mining

http://www.argylediamonds.com.au

L: Block cave 250 m deepC: Underground entranceR: Haul trucks

Diamond formation: Primary deposits• Diamond recovery

-Millions of tons removed per year-Diamonds represent 1 part per million of host rock!

1,000,000 tons rock = 999,999 tons waste + 1 ton diamonds

-Processing:1. Gravity separation2. X-ray detection

-Waste1. Piled2. Covered and sealed “forever”

http://www.diavik.ca/ENG/ouroperations/1624_underground_mining_equipment.asp

Diamond formation: Secondary deposits• Alluvial (placer) deposits or “artisanal diamond mining”• Weathering of diamond-bearing pipes into water• Simple mining techniques

Zimbabwe

http://www.galdu.org/web/index.php?odas=5116&giella1=eng

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Diamond formation: Secondary deposits• International concerns:

-no regulatory framework-lack of safety measures-child labor-environmental degradation-prostitution in mining camps-spread of HIV/AIDS

-“...diamonds that originate from areas controlled by forces orfactions opposed to legitimate and internationally recognizedgovernments, and are used to fund military action in oppositionto those governments, or in contravention of the decisions of theSecurity Council”. UN

http://www.galdu.org/web/index.php?odas=5116&giella1=eng

Conflict diamonds, orBlood diamonds

Diamond formation: Secondary deposits• International concerns:

-no regulatory framework-lack of safety measures-child labor-environmental degradation-prostitution in mining camps-spread of HIV/AIDS

• Regulations, 2003-Kimberley ProcessCertification Scheme-US Clean Diamond Act

• 1% of diamonds sold today are conflict diamonds accordingto the World Diamond Council

http://en.wikipedia.org/w

iki/File:Kim

berly_Process_Map.svg

Conflict diamonds, orBlood diamonds

Diamond formation: Secondary deposits• Marine deposits

http://www.amnh.org/exhibitions/diamonds/marine.html

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US diamond mines• Murfreesboro, Arkansas discovery in 1906

-1 lamproite pipe-100,000 stones between 1907-1933

• Kelsey Lake, 1996-2002-8 kimberlite pipes-2 open pit mines

http://www.amnh.org/exhibitions/diamonds/marine.html

Diamonds and the environment

non-metallic resources: diamondsresources.seattlecentral.edu/faculty/kgagnon/env170/diamonds...

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