Minerals, Metals, and Other Materials

Rocks and Minerals

How is the star in star sapphires produced?

Sapphires are composed of gem-quality corundum (Al2O3). Color appears in sapphires when small amounts of iron and titanium are present. Star stapphires contain needles of the mineral rutile that will display as a six-ray star figure when cut in the unfaceted cabochon (dome or convex) form. The most highly prized star sapphires are blue. Black or white star sapphires are less valuble. Since a ruby is simply the red variety of corundum, star rubies also exist.


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