GEOLOGY & PLANETARY SCIENCE A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z                    HOME ABOUT CATEGORIES SITE MAP COPYRIGHT ADVERTISE CONTACT entire Web this site garnet Garnet. Credit: Mineral Information Institute Two series of common orthosilicate minerals: the pyralspite series and the ugradite series. It has the general formula MII3MIII2(SiO4)3, having six end-members. Garnet is found in metamorphic rocks and pegmatites as cubic crystals, rounded grains and granular masses. It is brittle, glassy, and occurs in many hues; some varieties (particularly the red form) are important as gemstones. Being hard it is also used as an abrasive. Hardness 6.5–7.5, relative density 4. It is popularly the birthstone for January. Related category    • GEOLOGY AND PLANETARY SCIENCE Also on this site: Encyclopedia of Alternative Energy & Sustainable Living Encyclopedia of History Transport Concepts & Designs (partner site) BACK TO TOP