Spinel

Real mineral · rare · MgAl₂O₄

Magnesium aluminium oxide forming octahedral crystals in metamorphic marbles and igneous rocks. Historically confused with ruby due to its similar red colour and geological associations. Lacks the asterism of corundum.

Identity

Formula

MgAl₂O₄

Chemical class

oxide

Mineral group

Chromite, Magnetite

Also known as

Balas ruby (archaic red spinel), Pleonaste (dark variety)

Crystallography

Crystal system

cubic

Habits

octahedral, massive

Fracture

conchoidal

Physical properties

Mohs hardness

8

Density

3.58 g/cm³

Luster

vitreous

Colors

red, pink, blue, purple, black, colorless, orange

Streak

white

Transparency

transparent, translucent

Geology

Origins

metamorphic, igneous

Host rocks

marble, gneiss, basalt

Associated minerals

Ruby, Corundum, Tourmaline, Garnet

Geography

Myanmar, Sri Lanka, Tajikistan, Vietnam, Tanzania

Classification

Rarity

rare

Gem quality

Yes

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