Zircon
Zircon (/ˈzɜːrkɒn, -kən/) is a mineral belonging to the group of nesosilicates and is a source of the metal zirconium. Its chemical name is zirconium(IV) silicate, and its corresponding chemical formula is ZrSiO4. An empirical formula showing some of the range of substitution in zircon is (Zr1–y, REEy)(SiO4)1–x(OH)4x–y. Zircon precipitates from silicate melts and has relatively high concentrations of high field strength incompatible elements. For example, hafnium is almost always present in quantities ranging from 1 to 4%. The crystal structure of zircon is tetragonal crystal system. The natural color of zircon varies between colorless, yellow-golden, red, brown, blue, and green.
| Zircon | |
|---|---|
A lustrous crystal of zircon perched on a tan matrix of calcite from the Gilgit District of Pakistan | |
| General | |
| Category | Nesosilicates |
| Formula (repeating unit) | zirconium silicate (ZrSiO4) |
| IMA symbol | Zrn |
| Strunz classification | 9.AD.30 |
| Crystal system | Tetragonal |
| Crystal class | Ditetragonal dipyramidal (4/mmm) H-M symbol: (4/m 2/m 2/m) |
| Space group | I41/amd (No. 141) |
| Unit cell | a = 6.607(1), c = 5.982(1) [Å]; Z = 4 |
| Identification | |
| Color | Reddish brown, yellow, green, blue, gray, colorless; in thin section, colorless to pale brown |
| Crystal habit | tabular to prismatic crystals, irregular grains, massive |
| Twinning | On {101}. Crystals shocked by meteorite impact show polysynthetic twins on {112} |
| Cleavage | {110} and {111} |
| Fracture | Conchoidal to uneven |
| Tenacity | Brittle |
| Mohs scale hardness | 7.5 |
| Luster | Vitreous to adamantine; greasy when metamict. |
| Streak | White |
| Diaphaneity | Transparent to opaque |
| Specific gravity | 4.6–4.7 |
| Optical properties | Uniaxial (+) |
| Refractive index | nω = 1.925–1.961 nε = 1.980–2.015, 1.75 when metamict |
| Birefringence | δ = 0.047–0.055 |
| Pleochroism | Weak |
| Fusibility | close to 2,550 °C depend on Hf,Th,U,H,etc... concentrations. |
| Solubility | Insoluble |
| Other characteristics | Fluorescent and radioactive, May form pleochroic halos, Relief: high |
| References | |
The name derives from the Persian zargun, meaning "gold-hued". This word is changed into "jargoon", a term applied to light-colored zircons. The English word "zircon" is derived from Zirkon, which is the German adaptation of this word. Yellow, orange, and red zircon is also known as "hyacinth", from the flower hyacinthus, whose name is of Ancient Greek origin.