star sapphire

synthetic gem

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July 14, 2026

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A star sapphire is a variety of sapphire that exhibits asterism, a star-like figure visible in reflected or transmitted light. This phenomenon is caused by minute, oriented crystals of rutile included within the sapphire. When these inclusions are arranged in specific patterns, they create a six-pointed star, most commonly seen in hexagonal or pseudohexagonal crystals like sapphire.12

Sapphire itself is a natural or synthetic variety of corundum (aluminum oxide) prized as a gemstone. While typically blue due to iron and titanium, it can occur in various colors. Star sapphires, along with other nontransparent varieties, are cut en cabochon (a convex, highly polished form) rather than faceted. Synthetic star sapphires are also produced, often featuring more regular and distinct stars than their natural counterparts.3

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Verneuil process
Synthetic corundum.
Star rubies and sapphires, first developed in 1947 in the United States, are made by adding one percent rutile (titanium oxide, TiO₂) to the starting powder, forming the boules in the usual manner, and then heat treating them at temperatures between 1,100° C and 1,500° C. The rutile…
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Star rubies and sapphires, first developed in 1947 in the United States, are made by adding one percent rutile (titanium oxide, TiO₂) to the starting powder, forming the boules in the usual manner, and then heat treating them at temperatures between 1,100° C and 1,500° C. The rutile…
Read More