The Probert Encyclopaedia of Rocks & Minerals

DIAMOND

Diamond (once known as adamant) is the hardest naturally occurring mineral and the most important of the gem stones. Diamonds occur in pale shades of several colours, deep shades are rare. Gem quality diamond is transparent, of an attractive colour, and without internal fractures or inclusions of other materials. It has a relative hardness of 10. In jewellery terms, diamonds are measured in carats, with one carat weighing 0.2 grams, so a five carat diamond weighs one gram.
Research Diamond