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Mineral

Corundum

kuh-RUN-dum
Oxide Minerals

Corundum is a crystalline form of aluminium oxide, Al2O3, that crystallizes with trigonal symmetry. Pure corundum is defined as 9 on the Mohs scale, so it can scratch almost all other minerals, and its density of 4.02 g/cm3 is unusually high for a transparent mineral made of such light elements. Traces of iron, titanium, vanadium and chromium give it color: chromium makes rubies red, sapphires show a range of colors depending on the transition metal present, and the rare padparadscha sapphire is pink-orange. Corundum occurs in mica schist, gneiss, some marbles and low-silica igneous rocks such as syenite, and it is common in stream and beach sands because it resists weathering. Emery, a black variety with no value as a gemstone, is widely used as an abrasive. The name comes from the Tamil word kurundam.

Facts
Formation Class
Oxide mineral (aluminium oxide), forming in aluminum-rich, silica-poor igneous and metamorphic rocks; its gem varieties, ruby and sapphire, crystallize in these same settings. 1
Chemical Formula
Al2O3 1
Hardness (Mohs)
9 1
Colour
Colourless or White 2
Colour
Grey or Black 2
Colour
Red or Pink 2
Colour
Orange or Yellow 2
Colour
Green 2
Colour
Blue or Purple 2
Lustre
Vitreous 2
Lustre
Adamantine 2
Rarity
Common 2
Classification
Strunz Class
Oxides and Hydroxides 1
Crystal System
Trigonal (Rhombohedral) 1
Use
Gemstone 1
Use
Industrial and Abrasive 1
Connections

Associated With

Gneiss, Materials

Corundum's own page names gneiss as a host rock in metamorphic terranes.

Source Corundum (Wikipedia)
Marble, Materials

Corundum's own page names some marbles as a host rock in metamorphic terranes.

Source Corundum (Wikipedia)
Mohs Hardness Scale, Concepts

Pure corundum is defined to have 9.0 on the Mohs scale.

Source Corundum (Wikipedia)
Pegmatite, Materials

Corundum's own page states it occurs as large crystals in pegmatites.

Source Corundum (Wikipedia)
Schist, Materials

Corundum's own page names mica schist as a host rock in metamorphic terranes.

Source Corundum (Wikipedia)
Syenite, Materials

Corundum's own page names low-silica syenite intrusives as an igneous occurrence.

Source Corundum (Wikipedia)

Caused By

Magmatism, Processes
Source Corundum (Wikipedia)
Metamorphism, Processes
Source EBSCO Research Starters: Metamorphic processes, rocks, and mineral deposits
Additional Source Corundum (Wikipedia)Geology and occurrence

Classified As

Oxide Minerals, Subcategories

Crystallizes In System

Trigonal Crystal System, Concepts

In Discipline

Mineralogy, Disciplines
Source Corundum (Wikipedia)
In the Other Atlases

Mineral Species Of

Blue Sapphire

Also in Divinity Atlas: of this mineral species.

Ruby

Also in Divinity Atlas: of this mineral species.

White Sapphire

Also in Divinity Atlas: of this mineral species.

Yellow Sapphire

Also in Divinity Atlas: of this mineral species.

Found In

Afghanistan

Also in Geography Atlas: where this subject is found.

Source Corundum (Wikipedia)Geology and occurrence
Quote, Geology and occurrence
Corundum for abrasives is mined in Zimbabwe, Pakistan, Afghanistan, Russia, Sri Lanka, and India.
Greece

Also in Geography Atlas: where this subject is found.

Source Corundum (Wikipedia)Geology and occurrence
Quote, Geology and occurrence
Emery-grade corundum is found on the Greek island of Naxos and near Peekskill, New York, US.
India

Also in Geography Atlas: where this subject is found.

Source Corundum (Wikipedia)Geology and occurrence
Quote, Geology and occurrence
Corundum for abrasives is mined in Zimbabwe, Pakistan, Afghanistan, Russia, Sri Lanka, and India.
Pakistan

Also in Geography Atlas: where this subject is found.

Source Corundum (Wikipedia)Geology and occurrence
Quote, Geology and occurrence
Corundum for abrasives is mined in Zimbabwe, Pakistan, Afghanistan, Russia, Sri Lanka, and India.
Russia

Also in Geography Atlas: where this subject is found.

Source Corundum (Wikipedia)Geology and occurrence
Quote, Geology and occurrence
Corundum for abrasives is mined in Zimbabwe, Pakistan, Afghanistan, Russia, Sri Lanka, and India.
Sri Lanka

Also in Geography Atlas: where this subject is found.

Source Corundum (Wikipedia)Geology and occurrence
Quote, Geology and occurrence
Corundum for abrasives is mined in Zimbabwe, Pakistan, Afghanistan, Russia, Sri Lanka, and India.
Zimbabwe

Also in Geography Atlas: where this subject is found.

Source Corundum (Wikipedia)Geology and occurrence
Quote, Geology and occurrence
Corundum for abrasives is mined in Zimbabwe, Pakistan, Afghanistan, Russia, Sri Lanka, and India.
Sources
1. Corundum (Wikipedia)
Wikimedia Foundation
  • Lead section
    Because of corundum's hardness (pure corundum is defined to have 9.0 on the Mohs scale), it can scratch almost all other minerals.
  • Lead section
    Corundum is a crystalline form of aluminium oxide (Al2O3) typically containing traces of iron, titanium, vanadium, and chromium.
  • Corundum (Wikipedia), body text
    Corundum crystallizes with trigonal symmetry in the space group R3c
  • Lead section
    Corundum has two primary gem varieties: ruby and sapphire. Rubies are red due to the presence of chromium, and sapphires exhibit a range of colors depending on what transition metal is present.
  • Associated With: Pegmatite, Article text
    Other occurrences are as masses adjacent to ultramafic intrusives, associated with lamprophyre dikes and as large crystals in pegmatites. It commonly occurs as a detrital mineral in stream and beach sands because of its hardness and resistance to weathering.
  • Associated With: Schist, Occurrence section
    Corundum occurs as a mineral in mica schist, gneiss, and some marbles in metamorphic terranes.
  • Associated With: Gneiss, Occurrence section
    Corundum occurs as a mineral in mica schist, gneiss, and some marbles in metamorphic terranes.
  • Associated With: Marble, Occurrence section
    Corundum occurs as a mineral in mica schist, gneiss, and some marbles in metamorphic terranes.
  • Associated With: Syenite, Occurrence section
    It also occurs in low-silica igneous syenite and nepheline syenite intrusives.
  • Caused By: Metamorphism, Geology and occurrence
    Corundum occurs as a mineral in mica schist, gneiss, and some marbles in metamorphic terranes.
  • Caused By: Magmatism, Geology and occurrence
    It also occurs in low-silica igneous syenite and nepheline syenite intrusives.
View the Source
2. minerals.net: Corundum
minerals.net
  • Color field
    Many colors, including blue, red, violet, pink, green, yellow, orange, gray, white, colorless, and black. Occasionally also multicolored or striped.
  • Luster field
    Vitreous to adamantine
  • About
    These are fairly common forms, and due to their great hardness and prevalence
View the Source
Wikidata: Corundum
Wikidata Q131777
EBSCO Research Starters: Metamorphic processes, rocks, and mineral deposits
EBSCO Research StartersCaused By: Metamorphism, Metamorphic mineral deposits
Quote, Caused By: Metamorphism, Metamorphic mineral deposits
Corundum forms during regional metamorphism of aluminum-rich shale protoliths.
View the Source
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