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 1
Rock types: Igneous Four types of igneous rocks Mafic minerals Contain iron and magnesium Felsic minerals No iron and magnesium Bowen s reaction series: arranged by temperature of formation http://csmres.jmu.edu/geollab/fichter/ignrx/introigrx.html Rock types: Igneous Classified by texture and color/composition slow = thousands to millions of years fast = days to weeks Texture Glassy Vesicular Aphanitic (fine grained) Phaneritic (coarse grained) Porphyritic (two grain sizes) Cooling History Very fast (hours) cooling; noncrystalline. Very fast cooling with rapid gas escape forming bubbles in the non-crystalline rock. Slow cooling; microscopic crystal growth. Very slow cooling; crystals grow to visible size. Two stage cooling; one slow underground creating visible phenocrysts, the second fast at the earth's surface producing a fine grained groundmass. Examples Obisdian Pumice, scoria Rhyolite, andesite, basalt Granite, diorite, gabbro Any aphanitic rock with the word porphyry http://csmres.jmu.edu/geollab/fichter/ignrx/introigrx.html 2
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Pegmatite 4
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Rock types: Igneous rock distribution http://csmres.jmu.edu/geollab/fichter/ignrx/introigrx.html Rock types: Igneous rock distribution http://csmres.jmu.edu/geollab/fichter/ignrx/introigrx.html 6
Diamond Graphite Composition: Carbon Carbon Hardness: Hardest known, 10 1.0 Electrically: Insulator Conductor Luster: High, dispersion of light Dull, metallic Uses: Gemstone, cutting Pencils, lubricant Carbon allotropes http://www.chem.ufl.edu/~itl/2041_u01/lectures/lec_h.html Kimberlite rock - Volatile rich (CO 2 & H 2 O) ultramafic rock - [Rarely] contains xenoliths (solid rocks incorporated into magma) of diamond http://www.diamond-all.com/diamond.html 7
Diamond formation Originate in Earth s mantle, 150 km deep (~90 miles) http://dao.mit.edu/8.231/carbon_phase_diagram.jpg Diatreme - 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 Kimberlite pipe Lamproite pipe (Older than 2.5 Byr) (Youngest 50,000 years) http://www.brc-diamondcore.com/s/technical.asp?reportid=282496 8
Kimberley mine -Dug without any machinery, 1871-1908 -460 m diameter by 1100 m deep -3 tons of diamonds were extracted South Africa 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 Open pit mine Siberia 9
Open pit mine South Africa Open pit mine Australia (Lamproite pipe, broader cone) Open pit mine Canada 10
Hydraulic mining -Jets of water loosen gem material -Sluices catch gravel slurry for inspection -Ended in 1960 s Strip mining -Similar to open pit mines but done in long strips -Strip one material is removed -Strip two material fills strip one... Bucket wheel excavator: moves material 100 m by 25 m deep per day http://apod.nasa.gov/apod/ap061122.html Underground mining Diavik open pit mine, Northwest Territories Canada 55 million year old pipe Planned 2012 transition to an underground mine Red: three kimberlite pipes Green/blue: planned mine network http://www.diavik.ca/eng/ouroperations/1624_underground_mining_equipment.asp 11
Underground mining L: Block cave 250 m deep C: Underground entrance R: Haul trucks http://www.argylediamonds.com.au 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 separation 2. X-ray detection -Waste 1. Piled 2. 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 12
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 Conflict diamonds, or Blood diamonds -...diamonds that originate from areas controlled by forces or factions opposed to legitimate and internationally recognized governments, and are used to fund military action in opposition to those governments, or in contravention of the decisions of the Security Council. UN http://www.galdu.org/web/index.php?odas=5116&giella1=eng 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 Process Certification Scheme -US Clean Diamond Act Conflict diamonds, or Blood diamonds 1% of diamonds sold today are conflict diamonds according to the World Diamond Council http://en.wikipedia.org/wiki/file:kimberly_process_map.svg Diamond formation: Secondary deposits Marine deposits http://www.amnh.org/exhibitions/diamonds/marine.html 13
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 14