This edition of RockTalk delves into the formation and mining history of diamonds in the west. Digital PDF download. RT-02-03D
From the Introduction:
WHAT ARE DIAMONDS?
Diamonds are formed from pure carbon, one of the most abundant elements on planet Earth. Diamonds, even from ancient times, have been sought for their extraordinary hardness (they are the hardest substance known) and their brilliance, especially in the colorless transparent gemstone variety. Ironically the other form of pure carbon is graphite, which is very soft with a soapy feel and a dull gray color. Graphite is commonly the “lead” in a pencil.