Sunday, 15 December 2013
Formula: Al2O3
System: Trigonal
Colour: Colourless, blue, red, ...
Hardness: 9
Member of: Hematite Group
Name: Named "corinvindum" in 1725 by John Woodward and derived from the Sanskrit, kuruvinda ("Ruby"). Richard Kirwan used the current spelling "corundum" in 1794. Known by many names in ancient times: adamant, sapphire, ruby, hyacinthos, asteria, etc.
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Occurrences of Corundum
Geological Setting: Silica-poor rocks, such as Nepheline-Syenites, alkali igneous undersaturated rocks, contact aureoles in altered aluminous shales, aluminous xenoliths in high temperature plutonic and hypabyssal rocks, metamorphosed bauxite deposits, and as a detrital material in sediments.
Physical Properties of Corundum
Lustre: Adamantine, Vitreous, Pearly
Diaphaneity (Transparency): Transparent, Translucent, Opaque
Colour: Colourless, blue, red, pink, yellow, grey, golden-brown
Streak: White
Hardness (Mohs): 9
Hardness Data: Mohs hardness reference species
Tenacity: Brittle
Cleavage: None Observed
Parting: Rhombohedral and basal parting {0001}, sometimes perfect but interrupted; also on {1011} due to exsolution (Boehmite), observed on large blocks (Georgia, USA).
Fracture: Irregular/Uneven, Conchoidal
Density (measured): 3.98 - 4.1 g/cm3
Density (calculated): 3.997 g/cm3
Diaphaneity (Transparency): Transparent, Translucent, Opaque
Colour: Colourless, blue, red, pink, yellow, grey, golden-brown
Streak: White
Hardness (Mohs): 9
Hardness Data: Mohs hardness reference species
Tenacity: Brittle
Cleavage: None Observed
Parting: Rhombohedral and basal parting {0001}, sometimes perfect but interrupted; also on {1011} due to exsolution (Boehmite), observed on large blocks (Georgia, USA).
Fracture: Irregular/Uneven, Conchoidal
Density (measured): 3.98 - 4.1 g/cm3
Density (calculated): 3.997 g/cm3
Chemical Properties of Corundum
Formula: Al2O3
Essential elements: Al, O
All elements listed in formula: Al, O
Analytical Data: Al (52.93)
O (47.07)
Empirical Formula: Al2O3
Common Impurities: Cr,Fe,V,Ti
Essential elements: Al, O
All elements listed in formula: Al, O
Analytical Data: Al (52.93)
O (47.07)
Empirical Formula: Al2O3
Common Impurities: Cr,Fe,V,Ti
Read more : Geologypage
More photo
This sample of corundum is from Franklin, New Jersey and is about 10 cm across.
These samples of corundum are displayed in the Smithsonian Museum of Natural History.
The sample is about 6 cm across and is from Franklin, New Jersey.
Corundum (var: “Ruby”) from Hunza Valley, Gilgit District, Gilgit-Baltistan (Northern Areas), Pakistan
Locality: Hunza Valley, Gilgit District, Gilgit-Baltistan (Northern Areas), PakistanSpecimen Size: 6.8 x 6.3 x 5.3 cm (small cabinet)
Corundum var. Ruby - Ambahatraso- Hiosy - Madagascar
Specimen weight:60 gr.Crystal size:1,2 cm tall
Overall size: 42mm x 30 mm x 38 mm
| Corundum (variety: “Sapphire”) (“Floater”) from Ratnapura, Sabaragamuwa Province, Sri Lanka Locality: Ratnapura, Sabaragamuwa Province, Sri LankaSpecimen Size: 1.4 x 0.6 x 0.5 cm (thumbnail) |
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