Corundum gemstone

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Physical properties of corundum

Hardness:	9 out of 10 on the Mohs scale
Luster:	glass
Transparency:	transparent
Color:	blue, blue, red, yellow, brown, gray

Characteristics of corundum

Under the name "corundum" hides more than one precious stone. Corundum is a transparent mineral of high hardness (after diamond, corundum is the hardest gemstone). Corundums include rubies (they are transparent, red or pink), sapphires (transparent, blue and blue) and indigo sapphires (dark purple), chlorosapphires (green and dark green), leucosapphires (rare transparent crystals). There are also corundums with a star effect (asteria or star-shaped rubies, star-shaped sapphires) and the so-called "emery" (an opaque corundum stone).

Jewelry varieties of corundum:

• Ruby. Color - red, purple. Valued highly
• Ruby with asterism effect. Valued highly
• Sapphire. Color - blue, blue, violet. Valued highly
• Sapphire with asterism effect. Valued highly
• Padparadscha sapphire. Color - yellow, orange, peach. Valued highly
• Pink sapphire. Color - pink, deep pink
• Chlorosapphire. Color - green, yellow-green
• Polychrome sapphire. Color - a combination of blue with yellow, green with yellow, green with blue
• Leucosapphire. Colorless. Not highly valued
• Black sapphire. Color - dark gray. Almost opaque. Not highly valued

The word "corundum" itself most likely comes from the Indian "kauruntaka".

There are also separate names for some corundums. So, for example, earlier purple corundums were called "Bengal amethysts", red-violet corundums were called "amaldine sapphires", and transparent purple corundum was called "violet". Or, gemstone dealers added the epithet "oriental" to the names of stones to draw attention to the high quality of corundum - oriental emerald, oriental diamond, oriental aquamarine, oriental chrysolite and oriental topaz.

In addition to the manufacture of precious stones, corundum monoliths, emery, fine-grained corundums and corundum powders, due to their high strength, are used for grinding various metals, glasses and precious stones themselves.

Moreover, the use of corundum emery for processing hard materials has been known for a very long time. There is even a legend according to which Moses carved the ten commandments with corundum "shamir" (shamir - emery, fine-grained corundum) on a plate of solid lapis lazuli.

How much is corundum

Rubies are valued the highest among corundums - from $50 to $500 per 1 carat, depending on the quality. Large flawless rubies can reach a price of $ 1,500 per 1 carat. Sapphires are priced lower - from $40 to $400 per 1 carat. The very best stones can cost up to $1,200 per carat. Corundums with the effect of asterism are also highly valued. Roads and padparadscha sapphires - from $30 to $400 per 1 carat. Leucosapphires are the least valued - the price is from $10 to $150 per 1 carat, and black sapphires - from $5 to $50 per 1 carat.

In modern times, there are technologies for the artificial growth of corundum crystals.

	★ Rhinestone
See also:	★ Rubellite gemstone
	★ Morganite gemstone