Zircon (redirected from Matura Diamond)

zircon

Zircon with quartz from Cheyenne Canyon, Colorado

(credit: Courtesy of the Field Museum of Natural History, Chicago; photograph, John H. Gerard—EB Inc.)

Silicate mineral, zirconium silicate, ZrSiO₄, the principal source of zirconium. Zircon is widespread as an accessory mineral in acid igneous rocks; it also occurs in metamorphic rocks and, fairly often, in detrital deposits. It occurs in beach sands in many parts of the world, particularly Australia, India, Brazil, and Florida, and is a common heavy mineral in sedimentary rocks. Gem varieties occur in stream gravels and detrital deposits, particularly in Indochina and Sri Lanka, but also in Myanmar, Australia, and New Zealand. Zircon forms an important part of the syenite of southern Norway and occurs in large crystals in Quebec.

---

zircon

a reddish-brown, grey, green, blue, or colourless hard mineral consisting of zirconium silicate in tetragonal crystalline form with hafnium and some rare earths as impurities. It occurs principally in igneous rocks and is an important source of zirconium, zirconia, and hafnia: it is used as a gemstone and a refractory. Formula: ZrSiO₄

---

zircon [′zər‚kän]

(mineralogy)

ZrSiO₄A brown, green, pale-blue, red, orange, golden-yellow, grayish, or colorless neosilicate mineral occurring in tetragonal prisms; it is the chief source of zirconium; the colorless varieties provide brilliant gemstones. Also known as hyacinth; jacinth; zirconite.

---

Zircon 

(from the German Zirkon; original source, Persian zargun, “golden”), a mineral, a nesosilicate with the composition Zr[SiO₄]. Distinctions are made between zircons on the basis of impurity content: alvite contains hafnium and thorium, oyamalite contains transition metals and phosphorus, hagathalite contains transition metals and niobium, and naegite contains transition metals, thorium, niobium, and tantalum. Metamict dipyramidal zircons containing thorium, uranium, and water (Th > U) are called malacons, while prismatic zircons (Th < U) are called cyrtolites. Honey yellow, red-brown, and pink transparent zircons are called hyacinths. Metacolloidal, collomorphic zircons are called arshinovites.

Zircon crystallizes in the tetragonal system, forming tabular, short prismatic, or, less often, dipyramidal crystals. Regular concretions with xenotime, YPO₄, are frequent. Zircons are brownish yellow to brown, grayish, red, or pink; they may sometimes be colorless. Zircons are transparent to translucent. They usually exhibit no cleavage. Zircons have a hardness of 7–8 on Mohs’ scale and a density of 4,680–4,710 kg/m³ (in the metamict varieties, the hardness and density are less).

Zircon is a characteristic accessory mineral in granites and nepheline syenites and their effusive analogues, as well as of various metamorphic and terrigenous sedimentary rocks; large zircon deposits are found in granitic and alkaline pegmatites. Zircon sometimes concentrates in industrial quantities together with pyrochlore in zones of albitization of alkali rocks. Upon weathering of rocks containing zircon, the mineral may form alluvial deposits. Large reserves of zircon are found in the littoral-marine deposits on the Atlantic coast of the USA (Florida), on the island of Sri Lanka, and in eastern Australia.

Zircon is the major source for the production of zirconium, hafnium, and zirconium oxide (zirconium dioxide). Pure zircon sands are used in mold casting, as well as a starting material in the production of refractories and special ceramic materials. Hyacinth and transparent yellow and green zircons are used in jewelry-making (class II gems).

A. I. GINZBURG