CHARLES D. WINTERS / SCIENCE PHOTO LIBRARY CHARLES D. WINTERS / SCIENCE PHOTO LIBRARY
Uncut sapphire. Piece of uncut sapphire crystal. Sapphire is a blue, transparent variety of the mineral corundum (aluminium oxide, Al.O3). Small amounts of impurities, such as chromium, iron, or titanium give it its blue colour. In addition to their importance as highly prized gemstones, sapphires are used in industry as hard bearings in watches and scientific apparatus. They are found in Sri Lanka, Australia, USA and China.
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