3. Superior Hardness

Spinel is one of the hardest gems. Hardness is the resistance of a material to being scratched. A high hardness helps a gem resist abrasion without scratching. This is a very important property for gems that will be worn for years – or for a lifetime.

Today an increasing number of couples are selecting colored stones for their engagement jewelry. This should put spinel and its superior hardness in the spotlight.

alluvial spinel — **The Hardness of Spinel:** Spinel is one of the hardest and most durable minerals. That durability enables crystals of spinel to survive being weathered from the rock in which they crystallized, transported long distances by the current of a stream, and be deposited as water-worn particles in a stream sediment. Most spinels are found by artisanal miners who prospect stream sediments hoping to find a gem. The colorful spinels in this photo were mined from stream sediments in Vietnam. The deep red piece of spinel in the lower center of the image measures 7 millimeters by 5 millimeters.

Spinel has a hardness of 8 (out of a possible 10) on the Mohs hardness scale. The only commonly used gem minerals that exceed its hardness are: diamond (10); corundum, the mineral of ruby and sapphire (9); and chrysoberyl, the mineral of alexandrite, chrysoberyl, and cat’s-eye chrysoberyl (8 1/2). Topaz (8) and beryl, the mineral of emerald, aquamarine, morganite, and heliodor (7.5 to 8), are the only common gems that equal the hardness of spinel.

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3. Superior Hardness

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