The following products result: (1) diamond proper—distorted cubic crystalline gem-quality stones varying from colourless to red, pink, blue, green, or yellow; (2) bort—minute dark crystals of abrasive but not gem quality; (3) ballas—randomly oriented crystals of abrasive quality; (4) macles—triangular pillow-shaped crystals that are industrially useful; and (5) carbonado—mixed diamond–graphite crystallites containing other impurities.
It was later found to occur naturally in tiny amounts on Earth and in meteorites.
, “to write,” reflects its property of leaving a dark mark when rubbed on a surface.
Coal and coke, for example, are used extensively as fuels.
Charcoal is used as an absorptive and filtering agent and as a fuel and was once widely used as an ingredient in gunpowder.
Isolated finds around the world in regions where no sources are indicated have not been uncommon.