Corundum

Chemical formula (IMA record)

Al₂O₃

Recognition status

Grandfathered

Original-description year in master list

1714 ?

First-discovery country (IMA)

India ?

Crystal system

Trigonal (hexagonal setting)

Mohs hardness

9

Measured density

3.98–4.10 g/cm³ (measured range)

Historical discoverer

Not supplied in the IMA master list

How it occurs in nature

Corundum is associated with aluminium-rich, silica-poor environments. It occurs in certain igneous rocks and high-grade metamorphic rocks. Weathering can release crystals that subsequently accumulate in placer deposits.

Related gem names

Discovery & scientific record

The country refers to the master list’s first-discovery country, using modern borders. It is not a list of all deposits. A question mark is retained when the source is uncertain; a special-procedure date can refer to redefinition rather than discovery.

Catalog coverage and profile depth are different: every species in the cited IMA edition is indexed, but this edition does not provide every physical property or a full discovery narrative. The archive leaves those gaps explicit. Formulae and references are adapted from the IMA list under CC BY-SA 3.0; consult the original page for authoritative typography.