Asterism (gemology)
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An asterism is a star-shaped concentration of light reflected or refracted from a gemstone. It can appear when a suitable stone is cut en cabochon.
Asterism on the surface of a blue star sapphire.
Sapphire
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Sapphire is a precious gemstone, a variety of the mineral corundum, consisting of aluminium oxide with trace amounts of elements such as iron, titanium, cobalt, lead, chromium, vanadium, magnesium, bo
Asterism (gemology)
…is cut en cabochon (i.e. shaped and polished, not faceted). A gemstone that exhibits this effect is called a star stone or asteria. The best known is star sapphire, but many other minerals can also be asteria, usually due to impurities in the crystal structure. The archetypal asteria is the star sapphire, generally…
Main sapphire-producing countries
Teardrop-shaped blue sapphire
The 193.39 carat Star of Lanka star sapphire
Sapphire ring made c. 1940