Rubies

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What Makes a Ruby?
Rubies are gem corundums with a dominant red color. The color can range from orangy red to purplish red or brownish red. The most desirable color range is a pure vibrant red to a slightly purplish red.

The red color of ruby is produced by the presence of chromium in the gem. A small trace of chromium will produce a pink color. To be considered a ruby, there must be enough chromium to give the gem a distinctly red color.

Finally, rubies must have a combination of color and clarity that makes them an attractive gem. Opaque pieces of corundum with just a hint of red color are not rubies - they are common corundum. Ruby was discovered in 1902. {| class="wikitable"
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Physical Properties of Corundum

 * Chemical Classification
 * Oxide
 * Color
 * A gem corundum with a dominant red color is a ruby. Any other color of corundum is a sapphire.
 * Streak
 * Colorless (harder than the streak plate)
 * Luster
 * Adamantine to vitreous
 * Diaphaneity
 * Transparent to translucent
 * Cleavage
 * None. Corundum does display parting perpendicular to the c-axis.
 * Mohs Hardness
 * 9
 * Specific Gravity
 * 3.9 to 4.1 (very high for a nonmetallic mineral)
 * Diagnostic Properties
 * Hardness, high specific gravity, hexagonal crystals sometimes tapering to a pyramid, parting, luster, conchoidal fracture
 * Chemical Composition
 * Al2O3
 * Crystal System
 * Hexagonal
 * Uses
 * Historically used as an abrasive. Specimens with pleasing colors have a long history of gemstone use.
 * }
 * Diagnostic Properties
 * Hardness, high specific gravity, hexagonal crystals sometimes tapering to a pyramid, parting, luster, conchoidal fracture
 * Chemical Composition
 * Al2O3
 * Crystal System
 * Hexagonal
 * Uses
 * Historically used as an abrasive. Specimens with pleasing colors have a long history of gemstone use.
 * }
 * Uses
 * Historically used as an abrasive. Specimens with pleasing colors have a long history of gemstone use.
 * }