Corundum Archives - Cochise College Geology

Corundum

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Chemical Group: Oxide

Chemical Formula: Al₂O₃

Color: Gray, blue, pink, red, yellow, green, violet, black

Streak: White

Luster: Adamantine to vitreous

Transparency: Transparent to translucent

Hardness: 9 Specific Gravity: 4.0 to 4.1

Cleavage: Displays parting

Crystal Forms and Habits: Trigonal system. Most common form is a rough, barrel-shaped hexagonal prism.

Identifying Characteristics: Second hardest mineral

Uses: An abrasive, if low quality. If transparent and colorful, a gemstone: if red it is a ruby, other colors are sapphires.

Occurrences: Ontario, Canada, also Burma and Montana

Toxicity: When-swallowed: low When-inhaled: moderate

Additional Information: Corundum is simply aluminum oxide. The mineral corundum typically crystallizes in the form of hexagonal prisms with flat ends. The sides of these hexagonal prisms are often very rough and ragged. Only if the corundum is colorful and transparent will it be classified as ruby or sapphire.

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Photos

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Corundum - Brown Common Corundum Crystal In Matrix

Corundum - Sapphire - Blue And Yellow Spindle Shaped Crystals - Burma

Corundum - Common Corundum Crystal In Matrix

Corundum - Common Corundum Crystal In Matrix - Close View

corundum-rubies and sapphires-water worn small pebbles — Corundum - Rubies And Sapphires - Water Worn Small Pebbles

corundum-large brown crystal of common corundum — Corundum - Large Brown Crystal Of Common Corundum

corundum-common corundum-hexagonal prism crystals — Corundum - Common Corundum - Hexagonal Prism Crystals

Corundum - Ruby - Crystals — Corundum - Ruby Crystals

corundum-rubies-dark pink faceted gems — Corundum - Rubies - Dark Pink Faceted Gems

corundum-ruby-star ruby cabochons — Corundum - Ruby - Star Ruby Cabochons

corundum-ruby in green zoisite-Africa — Corundum - Ruby In Green Zoisite - Africa

corundum-sapphire-blue faceted gems — Corundum - Sapphire - Blue Faceted Gems

corundum-sapphire-blue spindle shaped crystals-Burma — Corundum - Sapphire - Blue Spindle Shaped Crystals - Burma

Corundum - Sapphire - Spindle Shaped Crystals

corundum-sapphire-light blue faceted gems — Corundum - Sapphire - Light Blue Faceted Gems

corundum-sapphire-spindle shaped crystals-Bburma — Corundum - Sapphire - Spindle Shaped Crystals - Burma

corundum-synthetic ruby faceted gems — Corundum - Synthetic Ruby Faceted Gems

corundum-sapphire-yellow faceted gems-Burma — Corundum - Sapphire - Yellow Faceted Gems - Burma

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