Corundum

Al2O3

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Second in hardness only to diamond, corundum is an aluminum oxide (Al2O3) with a Mohs hardness of 9. Its gem varieties are ruby, colored red by chromium, and sapphire, which covers all other colors. The mineral crystallizes in the trigonal system as tabular, prismatic, or bipyramidal crystals with an adamantine luster, a colorless streak, and no cleavage. Specific gravity ranges from 3.98 to 4.10. Corundum's extreme hardness makes it a widely used abrasive, and synthetic corundum serves in laser technology, while the finest natural crystals are cut as ruby and sapphire. Colors other than red span the full range of sapphire, from blue and yellow to pink and colorless.

Corundum is the second hardest natural mineral after diamond. Its gem varieties are ruby (red, colored by chromium) and sapphire (all other colors). Synthetic corundum is widely used as an abrasive and in laser technology.

Sistema Cristalino Trigonal
Classe Mineral 04 Oxides and Hydroxides
Dureza Mohs 9.0
Gravidade Específica 3.98-4.10
Cor Red (ruby), blue (sapphire), various colors
Brilho Adamantine
Traço Colorless
Clivagem None
Fratura Conchoidal to uneven
Transparência Transparent
Hábito Cristalino Tabular, prismatic, bipyramidal

Dureza Mohs

Mohs Hardness: 9,0 – 9,0
1 Soft10 Hard
Corundum has a Mohs hardness of 9 on the 1–10 mineral hardness scale.
Dureza Mohs Reference Mineral
1 Talc
2 Gypsum
3 Calcite
4 Fluorite
5 Apatite
6 Orthoclase
7 Quartz
8 Topaz
9 Corundum
10 Diamond

Sistema Cristalino

Trigonal
Corundum crystallizes in the Trigonal crystal system.
Propriedade Value
Sistema Cristalino Trigonal (Rhombohedral)
Axial Relationships a = b = c, α = β = γ ≠ 90°

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Frequently Asked Questions

What is the hardness of Corundum?
Corundum has a Mohs hardness of 9.0.
What crystal system does Corundum belong to?
Corundum crystallizes in the Trigonal crystal system.
What color is Corundum?
Corundum is typically Red (ruby), blue (sapphire), various colors.
What type of luster does Corundum have?
Corundum exhibits a Adamantine luster.
What is the chemical formula of Corundum?
The chemical formula of Corundum is Al2O3.