Ever since the Pharaohs, men have been getting cleverer & cleverer at making imitation gems. Almost every precious stone now has a man-made twin. Last week the Linde Air Products Co. (a unit of Union Carbide & Carbon Corp.) announced that it had finally produced "star" sapphires and rubies.
Ordinary sapphires and rubies are clear crystals of aluminum oxide (A12O2). The colors come from small amounts of such elements as chromium or iron. For years, both gems have been manufactured (without the stars) by passing finely powdered A12O2 through the flame of an...
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