The Probert Encyclopaedia of Rocks & Minerals

GARNET

Garnet is a widely distributed group with several minerals. They are found in both metamorphic and igneous rocks. The chief use of red transparent garnets are as an inexpensive gem stone, however, much is used as an abrasive material. They have the formulae A3B2(SiO4)3 and a relative hardness of 8. The commonest colour of garnet is red and the lustre is vitreous. The dodecahedron and trapezohedron are the common forms. There are also white, green, yellow, brown, and black varieties. The garnet is a silicate, the bases being alumina lime (grossularite, essonite, or cinnamon stone), or alumina magnesia (pyrope), or alumina iron (almandine), or alumina manganese (spessarite), or iron lime (common garnet, melanite, allochroite), or chromium lime (ouvarovite, the colour emerald green). The garnet was, in part, the carbuncle of the ancients. Garnet is a very common mineral in gneiss and mica slate.
Research Garnet