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  3. Corundum

Corundum mineral - You can buy these samples

Corundum is a mineral on the Mohs hardness scale with a hardness of 9 - the hardest, excluding diamond. It occurs both in crystals and in large accumulations of granular masses, which are called emery. Red and blue transparent non-fractured varieties have separate names and are classified as gemstones. Due to chemical reasons, it cannot be found in association with quartz.

You can see corundum stone for sale and buy it in the Minerals of Russia online store.

Physical properties of Corundum

General
Category Oxide mineral – Hematite group
Formula
(repeating unit)		 Aluminium oxide, Al2O3
IMA symbol Crn
Strunz classification 4.CB.05
Dana classification 4.3.1.1
Crystal system Trigonal
Crystal class Hexagonal scalenohedral (3m)
H-M symbol: (3 2/m)
Space group R3c (No. 167)
Unit cell a = 4.75 Å, c = 12.982 Å; Z = 6
Identification
Color Colorless, gray, golden-brown, brown; purple, pink to red, orange, yellow, green, blue, violet; may be color zoned, asteriated mainly grey and brown
Crystal habit Steep bipyramidal, tabular, prismatic, rhombohedral crystals, massive or granular
Twinning Polysynthetic twinning common
Cleavage None – parting in 3 directions
Fracture Conchoidal to uneven
Tenacity Brittle
Mohs scale hardness 9 (defining mineral)
Luster Adamantine to vitreous
Streak Colorless
Diaphaneity Transparent, translucent to opaque
Specific gravity 3.95–4.10
Optical properties Uniaxial (−)
Refractive index nω = 1.767–1.772
nε = 1.759–1.763
Pleochroism None
Melting point 2,044 °C (3,711 °F)
Fusibility Infusible
Solubility Insoluble
Alters to May alter to mica on surfaces causing a decrease in hardness
Other characteristics May fluoresce or phosphoresce under UV light
Major varieties
Sapphire Any color except red
Ruby Red
Emery Black granular corundum intimately mixed with magnetite, hematite, or hercynite
Corundum
Code: 419
Corundum
Mountain Black, Raj-Iz, Polar Urals, RF
90*54*55mm

0.00 $ $200.00

Corundum
Code: 420
Corundum
Mountain Black, Raj-Iz, Polar Urals, RF
62*61*41mm

0.00 $ $133.33

Chloritoid, Corundum
Code: 1073
Chloritoid, Corundum
Irtyash deposit, Kaslinsky district, Chelyabinsk region, South Ural, RF
97*60*34mm

0.00 $ $40.00

Chloritoid, Corundum
Code: 1075
Chloritoid, Corundum
Irtyash deposit, Kaslinsky district, Chelyabinsk region, South Ural, RF
51*30*20mm

0.00 $ $18.33

Corundum
Code: 1270
Corundum
Mountain Black, Raj-Iz, Polar Urals, RF
30*20*18mm

0.00 $ $6.00

Corundum
Code: 1928
Corundum
Koltashi, Middle Urals, RF
35mm

0.00 $ $6.00

Corundum (UV)
Code: 4808
Corundum (UV)
Hit Island, Karelia, RF
33*32*30mm

0.00 $ $60.00

Corundum (UV)
Code: 4809
Corundum (UV)
Hit Island, Karelia, RF
36*30*21mm

0.00 $ $30.00

Corundum
Code: 4504
Corundum
Hit Island, Karelia, RF
37*27*29mm

0.00 $ $23.33

Corundum
Code: 4478
Corundum
Hit Island, Karelia, RF
35*27*25mm

0.00 $ $15.00

Corundum
Code: 4314
Corundum
Hit Island, Karelia, RF
28*17*16mm

0.00 $ $15.00

Corundum
Code: 3623
Corundum
Hit Island, Karelia, RF
41*33*26mm

0.00 $ $28.33

Corundum (UV)
Code: 3624
Corundum (UV)
Hit Island, Karelia, RF
37*33*21mm

0.00 $ $46.67

Corundum (UV), Almandine garnet (sphere)
Code: 3604
Corundum (UV), Almandine garnet (sphere)
Hit Island, Karelia, RF
52mm

0.00 $ $130.00

Corundum
Code: 2741
Corundum
Mountain Black, Raj-Iz, Polar Urals, RF
20*11*11mm

0.00 $ $11.67

Chloritoid, Corundum archived
Code: 1072
Chloritoid, Corundum
Irtyash deposit, Kaslinsky district, Chelyabinsk region, South Ural, RF
99*67*52mm

0.00 $ $31.67

Corundum archived
Code: 1272
Corundum
Hit Island, Karelia, RF
22*15*18mm

0.00 $ $28.33

Corundum archived
Code: 1387
Corundum
Mountain Black, Raj-Iz, Polar Urals, RF
26*20*31*mm

0.00 $ $6.00

Corundum archived
Code: 1704
Corundum
Hit Island, Karelia, RF
25*17*20mm

0.00 $ $45.00

Corundum archived
Code: 1741
Corundum
Hit Island, Karelia, RF
25*19*15mm

0.00 $ $15.00

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