zirconi

Zirconi is the term used to refer to zircons, the mineral group and its gemstone crystals. The principal mineral is zircon, with the chemical formula ZrSiO4, and it occurs in a wide range of igneous and metamorphic rocks as well as in sedimentary deposits where it has survived weathering. Zircons are valued both as gemstones and as a source of zirconium for industrial uses.

Physical and crystallographic properties are characteristic of the mineral. Zircon is a tetragonal silicate mineral that typically forms prismatic crystals and has a hardness of about 7.5 on the Mohs scale. It is commonly colorless or pale, but trace impurities can produce brown, yellow, green, red, or other hues. Zircon crystals can be highly refractive and may exhibit strong dispersion, contributing to their brilliance when cut as gemstones. The mineral exhibits relatively high density and generally shows two directions of poor cleavage.

Occurrences and deposits are widespread. Notable sources include Australia, Myanmar, Sri Lanka, Cambodia, and parts of Africa and the Americas. Zircon is frequently mined from heavy-mineral sands and from primary ore deposits, where it occurs together with other accessory minerals. In addition to gem-quality crystals, zircon is a major source of zirconium for industrial applications.

Uses and significance are twofold. Gem-quality zircons are used in jewelry and can resemble other gemstones in appearance, while industrially, zircon and zirconium compounds are employed in ceramics, refractories, and as a source material for zirconium metal and alloys. It is important to distinguish natural zircon from synthetic cubic zirconia, which is a diamond simulant.

See also: Zircon, Zirconium.