Topaz
| Topaz | |
|---|---|
Topaz crystal on white matrix | |
| General | |
| Category | Nesosilicate |
| Formula | Al2SiO4(F, OH)2 |
| IMA symbol | Tpz |
| Strunz classification | 9.AF.35 |
| Crystal system | Orthorhombic |
| Crystal class | Dipyramidal (mmm) H–M symbol: (2/m 2/m 2/m) |
| Space group | Pbnm |
| Unit cell | a = 4.65 Å, b = 8.8 Å, c = 8.4 Å; Z = 4 |
| Identification | |
| Color | Colorless (if impurities are absent), white, blue, brown, orange, gray, yellow, yellowish brown, green, pink, reddish pink, or even red |
| Crystal habit | Prismatic crystal |
| Twinning | Rarely on [111] |
| Cleavage | [001] Perfect |
| Fracture | Subconchoidal to uneven |
| Mohs scale hardness | 8 (defining mineral) |
| Luster | Vitreous |
| Streak | White |
| Diaphaneity | Transparent |
| Specific gravity | 3.49–3.57 |
| Optical properties | Biaxial (+) |
| Refractive index | nα = 1.606–1.629 nβ = 1.609–1.631 nγ = 1.616–1.638 |
| Birefringence | δ = 0.010 |
| Pleochroism | Weak in thick sections X = yellow; Y = yellow, violet, reddish; Z = violet, bluish, yellow, pink |
| Ultraviolet fluorescence | Golden yellow under short UV; cream under long UV |
| References | |
Topaz is a silicate mineral made of aluminum and fluorine with the chemical formula Al2SiO4(F, OH)2. It is used as a gemstone in jewelry and other adornments. Common topaz in its natural state is colorless, though trace element impurities can make it pale blue or golden-brown to yellow-orange. Topaz is often treated with heat or radiation to make it a deep blue, reddish-orange, pale green, pink, or purple.
Topaz is a nesosilicate mineral, and more specifically, an aluminosilicate mineral. It is one of the hardest naturally occurring minerals and has a relatively low index of refraction. It has the orthorhombic crystal system and a dipyramidial crystal class.
It occurs in many places in the world. Some of the most popular places where topaz is sourced are Brazil and Russia. Topaz is often mined in open pit or alluvial settings.