Zircon

Zircon
Zircon is a mineral belonging to the group of nesosilicates. Its chemical name is zirconium silicate and its corresponding chemical formula is ZrSiO4. Hafnium is almost always present in quantities ranging from 1 to 4%. The crystal structure of zircon is tetragonal crystal class. The natural color of zircon varies between colorless, yellow-golden, red, brown, and green. Colorless specimens that show gem quality are a popular substitute for diamond; these specimens are also known as "Matura diamond". It is not to be confused with cubic zirconia, a synthetic substance with a completely different chemical composition.

The name either derives from the Arabic word zarqun, meaning vermilion, or from the Persian zargun, meaning golden-colored. These words are corrupted into "jargoon", a term applied to light-colored zircons. Yellow zircon is called hyacinth, from a word of East Indian origin; in the Middle Ages all yellow stones of East Indian origin were called hyacinth, but today this term is restricted to the yellow zircons.

Zircon is regarded as the traditional birthstone for December.

General
Category Mineral
Chemical formula zirconium silicate ZrSiO4
Identification
Color brown, red, yellow, green, black, and colorless
Crystal habit dipyramidal prismatic
Crystal system Tetragonal; 4/m 2/m 2/m
Cleavage indistinct, two directions
Fracture Subconchoidal to uneven - brittle
Mohs Scale hardness 7.5
Luster Adamantine
Refractive index nω=1.967 - 2.015 nε=1.920 - 1.960
Birefringence δ=0.047 - 0.055
Streak White
Specific gravity 4.6–4.7
Fusibility Infusible
Solubility Insoluble
Other Characteristics Fluorescent and radioactive