Diamonds 01 31 2014 Diamond Origin of name and early legend From Old French diamant after Greek and Latin adamas meaning invincible unconquerable Originally adamas usually referred to iron or iron alloy About A D 50 Ovid used adamas in the sense of a diamond By A D 70 Pliny the Elder described diamonds testing diamond resisted the blow of an iron hammer This early belief is not true Many diamonds were shattered by miners in India and South Africa 1400s 1800s Diamond Characteristics Composition Pure Carbon C Hardness 10 Colors Colorless many others Streak White Specific Gravity SG 3 52 Refractive Index RI 2 42 dispersion 0 044 high lots of fire Crystals cubic systems often octahedrons or cubes Luster Adamantine Diamonds are less shiny than glass Formation of Diamonds Form near the core mantle boundary Depth 2900 Km 1800 miles High pressure and temperature conditions 900 1300 degrees Diamonds are carried to the surface as inclusions in pipes of Celsius 45 to 60 kilobars volcanic rock and erupted o Kimberlite or lamproite peridotite an ultramafic rock o Types of volcanoes that is made of ultra heavy rock Diamond ages most are 990 million years many are 3 2billion o Kimberlite pipes are younger than the diamond inclusions in Graphite not diamond is the stable form of carbon at the Earth s o Diamond will burn or oxidize on the surface if dropped in a fire o If heated to bright red a diamond will catch fire and convert To avoid conversion to graphite diamonds must rise to the surface years old them surface for a short time CO2 gas rapidly o Probably travel 10 to 30 km hour part of the way o Near the surface the transport rate probably increases to several hundred km hour o Time needed to reach the surface 12 hours Why are diamonds so hard And why is graphite not Both are polymorphs of carbon Diamond Atoms are linked in a 3D network Graphite Atoms are linked in sheets o Little holds the sheets together so they easily slide past one another making the mineral soft Where were diamonds collected early in history Ancient times to at least 800 B C All diamonds came from alluvial gravels in India eroded from kimberlite pipes in the Mogok region is the most important region for gemstones in the Golconda area world 1725 Diamonds discovered in alluvial gravels of Brazil The South African Diamond Rush o 1859 Diamond discovered in alluvial gravels of South Africa Oil in PA Word Dinosaurs Origin of Species written o 1867 First authenticated find o 1870 Diamonds discovered in kimberlite pipes blue ground or yellow ground if weathered near Kimberley Ultramafic rock Kimberlite 1871 Diamonds discovered on the de Beers farm resulted in a large mine called the Big Hole Diamonds on the beaches Africa now Namibia o 1908 Diamonds discovered in beach sands of South West More than 80 of diamonds from west African beaches Natural faces of diamonds are slightly bowed out in the are of gem quality cubic system o In Africa diamonds are mined from kimberlite pipes alluvial gravels or beach sands in Botswana South Africa Democratic Republic of Congo Ghana Guinea Sierra Leone Angola Tanzania and Namibia Where are diamonds mined now Until recently Africa accounted for 98 of diamond production o Africa not accounts for 50 Australia lamproite pipe and Russia kimberlite pipe are now large diamond producers Other sources Venezuela China Canada USA o American diamonds occasionally found in gravels some are in ultramafic pipes ex Murfreesboro Arkansas De beers England South Africa o 1870 Cecil Rhodes arrived in Durban South Africa from o 1873 Bought a claim in the de Beers mine at Kimberley o 1880 Rhodes formed the De Beers Mining Co Ltd o 1888 Rhodes formed De Beers Consolidated Mines Ltd To control diamond mining and control diamond output Began limiting sales of diamonds to stabilize prices Established a syndicate of diamond buyers in Kimberley and London Formalized the process of equating the supply to demand the basic principle of economics Syndicate s marketing policy was largely successful until increasing diamond production from western Africa increased and diamond prices slumped in the 1890 s o 1890 Rhodes elected Prime Minister of South Africa died in o 1902 Ernest Oppenheimer arrived in Kimberley as a diamond 1902 buyer o 1917 Oppenheimer set up the Anglo American Corporation to exploit gold fields in the east Rand South Africa Became Chairman of De Beers 1929 o In the mid 1920s new diamond discoveries in western Africa plus high production costs at Kimberley caused falling prices o 1929 Great Depression began Diamond market collapsed syndicate had deep financial problems Oppenheimer formed the Diamond Corporation to help stabilize prices through a single sales channel 1933 De Beers could not cover operating expenses closed mines at Kimberley in 1934 o To counteract these conditions Oppenheimer persuaded producers in all countries that one production and sales channel would cushion the diamond trade against boom and bust cycles De Beers in cooperation with the South African government led producers to form the Diamond Producers Association DPA o 1957 Oppenheimer died but policies continued De Beers Production and Marketing Strategy DPA Formulates policy and sets quotas o Comprises De Beers in South Africa and Namibia Diamond Corporation a De Beers subsidiary government of South Africa which owns some mines o DPA makes marketing agreements with outside producers through the Diamond Corporation Central Selling Organization CSO Group of marketing companies diamond producers cooperatively sell diamonds o Diamonds are first sent to the DPA Johannesburg or the Diamond Corporation London o Sorted into gem and industrial quality stones and the sold through different organizations Rough gem diamonds are sold via the Diamond Purchasing and Trading Company to the Diamond Trading Company o Parcels of fixed price are offered to buyers at 10 sales sights per year o Rough diamonds then make their way to gem cutters The CSO controls 60 80 of the world s legal trade in diamonds o Prices are controlled by stockpiling goods when demand is low forcing prices to remain high and incrementally increasing the price when demand is high De Beers was for a long time been prohibited from directly selling diamonds in the USA by the Sherman Antitrust Act Diamond Sales Outside the CSO The CSO does not normally handle sales of diamond rough from Ghana Sierra Leone D R Congo Ivory Coast Guinea India Brazil Venezuela Guyana and some small