zircon Mineral, ZrSiO₄; sp. gr. 4.6; hardness 7.5; tetragonal; most commonly light brown or reddish-brown, but sometimes grey, yellow, or green; vitreous lustre; crystals usually square prisms with bipyramidal terminations; cleavage prismatic, indistinct {110} and poor {111}; one of the most widely distributed accessory minerals in igneous rocks (e.g. granite, syenite, and pegmatites), when the crystals can be quite large, also occurs in metamorphic rocks (e.g. gneisses and schists), and concentrated in detrital beach and river sands. It is the main source of zirconium metal. Common zircon is used extensively in the foundry industry.

zircon Orthosilicate mineral, zirconium silicate (ZrSiO₄), found in igneous and metamorphic rocks and in sand and gravel. It displays prismatic crystals. It is usually light or reddish brown, but can be colourless, grey, yellow or green. It is used widely as a gemstone because of its hardness and high refractive index. Hardness 7.5; r.d. 4.6.

zir·con / ˈzərˌkän/ • n. a mineral occurring as prismatic crystals, typically brown but sometimes in translucent varieties of gem quality. It consists of zirconium silicate and is the chief ore of zirconium.

zircon (min.) native silicate of the metallic element zirconium. XVIII. — G. zirkon.