Topaz

Real mineral · uncommon · Al₂SiO₄(F,OH)₂

Aluminium silicate fluoride found primarily in granitic pegmatites. Its perfect basal cleavage makes it prone to splitting along flat planes parallel to the base. The imperial orange-pink variety is among the rarest gemstone colours.

Identity

Formula

Al₂SiO₄(F,OH)₂

Chemical class

silicate

Also known as

Imperial topaz (golden-orange), Blue topaz

Crystallography

Crystal system

orthorhombic

Habits

prismatic, columnar

Fracture

subconchoidal

Physical properties

Mohs hardness

8

Density

3.57 g/cm³

Luster

vitreous

Colors

colorless, blue, yellow, pink, orange, brown

Streak

white

Transparency

transparent, translucent

Geology

Origins

igneous

Host rocks

pegmatite, granite, rhyolite

Associated minerals

Quartz, Beryl, Tourmaline, Fluorite

Geography

Brazil, Pakistan, Russia, USA, Sri Lanka

Classification

Rarity

uncommon

Gem quality

Yes

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