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 zircon Zircon crystals. Credit: NSF A hard silicate mineral (ZrSiO4), a major ore of zirconium of widepsread occurrence. Zircon forms prismatic crystals in the tetragonal system, which when transparent are used as gems. They may be colorless, red, orange, yellow, green, or blue, and have a high refractive index. 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