Smoky Quartz

Real mineral · common · SiO₂

Brown to black quartz coloured by natural irradiation of aluminium-bearing defects in the crystal lattice. Colour can be removed by heating above 300°C. The morion variety is nearly opaque black.

Identity

Formula

SiO₂

Chemical class

silicate

Mineral group

Amethyst, Bloodstone, Carnelian, Chalcedony, Citrine, Quartz, Rose Quartz, Tiger's Eye

Also known as

Cairngorm (Scottish variety), Morion (very dark black variety)

Crystallography

Crystal system

trigonal

Habits

prismatic

Fracture

conchoidal

Physical properties

Mohs hardness

7

Density

2.65 g/cm³

Luster

vitreous

Colors

brown, gray, black, brownish black

Streak

white

Transparency

transparent, translucent

Geology

Origins

igneous, hydrothermal

Host rocks

granite, pegmatite, schist

Associated minerals

feldspar, Mica, Tourmaline

Geography

Brazil, Scotland, Switzerland, USA, Madagascar

Classification

Rarity

common

Gem quality

Yes

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