Properties of Topaz

Topaz is a silicate mineral with the chemical formula Al2(SiO4)(F,OH)2. It belongs to the orthorhombic crystal system and is often found in igneous rocks, as well as in cavities in granites and rhyolites.

Image of topaz mineral
Credit: Géry PARENT, Public domain, via Wikimedia Commons

The following table provides a comprehensive list of topaz properties in both SI and US customary/Imperial units at normal temperature and pressure (NTP).

Note: click on the icon to switch between Metric and Imperial units.

Table of Topaz Properties
Physical Properties
Metric
Chemical FormulaAl2(SiO4)(F,OH)2
Molar Mass182.25 g/mol
Crystal SystemOrthorhombic
Mohs Hardness8
Density3490 - 3570 kg/m3
ColorColorless, pale blue, yellow, yellowish brown, or red
DiaphaneityTransparent
LusterVitreous (glassy)
Cleavage(001) perfect
FractureUneven, brittle
StreakWhite

Note: unless stated otherwise, all values are taken at room temperature (approximately 20°C or 68°F) and 1 atm pressure. (1 atm = 101,325 Pa)

Related Pages
References: 1) Cardarelli, François. Materials Handbook: A Concise Desktop Reference. Switzerland: Springer International Publishing, 2018. 2) CRC Handbook of Chemistry and Physics, 97th Edition. United Kingdom: CRC Press, 2016-2017.