Word: alumina
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...Silverman, head of the Chemistry Department of the University of Pittsburg, an authority on glass, ceramics and gems, says that synthetic jewels of as good practical and esthetic value as the natural gems are now being made in quantity. Artificial rubies and sapphires of various colors are made from alumina, by the addition of varying chromic or ferric oxides. They sell at $2.00 a carat...