Diamond

The hardest substance known to man, diamonds are a crystalline form of pure carbon. Prior to modern day discoveries in Brazil and South Africa, the only known source of diamonds was India. In ancient times diamonds were called adamant, meaning "indestructable".

See also:

• Diamond according to Maplet's A Greene Forest

References:

• Cariadoc's "On gemstones"
• Walter Schumann, Gemstones of the World, New York, (rev) 1997