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Mineralpedia Details for Corundum

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Corundum

Corundum

Likely named after the Sanskrit word for ruby, kurivinda, through the Tamil word kurundam. Hexagonal, prismatic, and sectorially striated crystals that can also occur in granular and massive forms. Corundum forms in a variety of colors including clear, gray, brown, pink to blood red, orange, yellow, green, blue to cornflower, and violet. Characteristically in Al-rich, Si-poor environments including in syenite and monzonite. It also occurs in high grade metamorphics and as detritus in placer deposits. It is found in numerous, worldwide localities.

c 2001-2005 Mineral Data Publishing

See also Handbook of Mineralogy, Anthony et al (1995) and MSA at http://www.handbookofmineralogy.org/pdfs/corundum.pdf

Formula
Al2O3 
Crystal System
Trigonal 
Crystal Habit
Euhedral Crystals, Tabular, Prismatic 
Cleavage
None, None, None 
Luster
Vitreous (Glassy) 
Color
blue, red, yellow, brown, gray 
Streak
none 
Class
Trigonal - Hexagonal Scalenohedral 
Fracture
Tough 
Hardness
WebMineral
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Mindat
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Corundum var. Sapphire from Passara, Uva Province, Sri Lanka

Corundum var. Sapphire
            from Passara, Uva Province, Sri Lanka

Sapphire crystal showing good striations and inclusions of a blue mineral. Overall 4 x 2 x 1.4cm.

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Corundum var. Sapphire from Balangoda, Sabaragamuwa, Sri Lanka

Corundum var. Sapphire
            from Balangoda, Sabaragamuwa, Sri Lanka

Doubly terminated, yellow crystal, slightly water worn. Overall 6 x 2.5 x 2.5cm.

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Corundum var. Ruby from Bajouri, Hassanabad, Hunza, Northern Areas, Pakistan

Corundum var. Ruby
            from Bajouri, Hassanabad, Hunza, Northern Areas, Pakistan

Prismatic deep red crystal with several nice faces to 2cm of Ruby Corundum.

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Corundum var. Ruby from Jagdalik, Kabul Prov., Afghanistan

Corundum var. Ruby
            from Jagdalik, Kabul Prov., Afghanistan

Well formed Ruby crystal to 1.8cm nicely exposed from white marble matrix.

Well formed Ruby crystal showing several good faces to 1cm.

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Corundum var. Ruby from Fiskenaes, Nuuk, Kitaa Province, Greenland

Corundum var. Ruby
            from Fiskenaes, Nuuk, Kitaa Province, Greenland

Bright red, crude crystals of Ruby to 2mm throughout matrix.

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Corundum from York River Skarn, Hastings Co., Ontario, Canada

Corundum
            from York River Skarn, Hastings Co., Ontario, Canada

A large blue-gray tapered Corundum crystal partially embedded in Biotite-Quartz matrix with one terminated end.

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Corundum from Miass, Southern Urals, Russia

Corundum
            from Miass, Southern Urals, Russia

Rich blue large Corundum crystal showing twinning patterns and two crystal faces.

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Corundum var. Ruby from Keivy Mountains, Kola Peninsula, Murmanskaja Oblast', Russia

Corundum var. Ruby
            from Keivy Mountains, Kola Peninsula, Murmanskaja Oblast', Russia

Small ruby crystal to 8mm.

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Corundum var. Ruby from Kola Peninsula, Russia

Corundum var. Ruby
            from Kola Peninsula, Russia

Thumbnail ruby with a single crystal to 1.5cm.

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Corundum var. Ruby from Kleggasen Ruby quarry, Froland, Aust-Agder, Norway

Corundum var. Ruby
            from Kleggasen Ruby quarry, Froland, Aust-Agder, Norway

Large ruby crystal to 3cm.

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Corundum from Sterling Hill mine, Ogdensburg, Sussex Co., New Jersey, United States

Corundum
            from Sterling Hill mine, Ogdensburg, Sussex Co., New Jersey, United States

A good representative specimen of altered country rock with red ruby crystals to 8mm, greenish Margarite and deep red Rutile.

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Corundum from Mundarara mine, Longido, Mt. Kilimanjaro, Tanzania

Corundum
            from Mundarara mine, Longido, Mt. Kilimanjaro, Tanzania

Deep, bright red 2cm crystal grains in green Zoisite matrix.

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Corundum from Zazafotsy quarry, Ihosy dist., Horombe, Fianarantsoa, Madagascar

Corundum
            from Zazafotsy quarry, Ihosy dist., Horombe, Fianarantsoa, Madagascar

A nice bluish purple prismatic sapphire Corundum crystal nicely exposed in biotite schist. The crystal is 3cm long and carries good luster but does not have color changing characteristics. There is a bit of a red zone at the center. Corundum is a good example of a high to medium-pressure metamorphism at high temperature. At this locality it occurs in metapelite, a metamorphosed fine-grained sedimentary rock.

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Corundum from Bancroft, Ontario, Canada

Corundum
            from Bancroft, Ontario, Canada

Greyish blue large crystal of Corundum 3.5cm across. with a few smaller in granitic matrix.

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Corundum from Ceylon, Sri Lanka

Corundum
            from Ceylon, Sri Lanka

Blue twinned, excellent small crystal.

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Corundum from Chester Emery mines, Hampden Co., Massachusetts, United States

Corundum
            from Chester Emery mines, Hampden Co., Massachusetts, United States

Emery is Corundum mixed with Magnetite, thus the magic magnet.

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