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Donald Haack, 78, diamond expert, adventurer, author and founder of Donald Haack Diamonds & Fine Gems in Charlotte passed away peacefully on Sunday, March 1, 2009
Diamond Memoirs
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ROUGH DIAMONDS
When unearthed, most diamonds appear roughly rounded with perhaps a hint of regular crystal form. Many are colorless, but most are pale shades of yellow; red, orange, green, blue, brown, and even black diamonds are also found.
Raw, uncut stones lack the exuberance of jewelry-store gems and can appear quite ordinary; Brazilian gold miners of the 18th century cast aside a fortune in unrecognized diamonds while panning for the precious metal. Diamond's familiar ornamental role represents a relatively recent development - a consequence in part of scientists' growing understanding of the nature of light.
On average, 250 tons of ore must be mined and processed to produce a one carat diamond of gem quality. When the mining operation is completed, sorters look at rough diamonds, separating them into small piles by shape, size, and quality, a long and laborious process.
Diamond crystallizes in the cubic system and its crystalline shapes are thus numerous, the principal ones are:
Octahedron
Dodecahedron
Cube
Rhombododecahedron
After a diamond is recovered, it is sorted according to certain categories:
Diamonds for cleavage.
Diamonds for sawing.
Diamonds for cutting.
Industrial diamonds.
Rough diamond can be sorted according to 3 distinct categories:
Gem quality.
Industrial quality.
Crushing-boart or boart.
Only 20% of the world production of rough diamonds are intended for the jewellery (gem quality) and 80% for the industrial uses.


This diamond cluster consists of at least a half-dozen distinct crystals, which individually appear to be slightly distorted octahedrons. The resulting shape is quite complex. Their color varies, too, mostly a gray, but some have a hint of green or brown, one appears white, and there is part of one exposed that is a dark silvery-gray. The really unusual thing about this specimen is that there is quite a bit of damage present (and it is difficult to damage a diamond). It appears that several additional crystals were part of the cluster, but broke off during the mining operation. There are two clean cleavage planes, plus two spots where other diamond crystals appear to have detached.
http://mineral.galleries.com/scripts/ item.exe?LIST+Minerals+Elements +Diamond
Links:
http://www.diamondrough.com
http://www.diamants-infos.com/en/rough/index.php? rub=rough_diamond_sorting
http://www.pbs.org/wgbh/nova/diamond/textindex.html