Texas blue topaz was designated the official state gemstone in 1969 and in 1977 the lonestar cut was also recognized as the official state gemstone cut..

The Lone Star Cut, designed by two native Texans, is a special gemstone cut that reflects a five-pointed star (the lone star of Texas). Topaz comes in all colors - a golden orange-yellow (called "imperial topaz") is considered the most valuable. Topaz is commonly thought of as a sky-blue gem, but a deep blue hue is rare in nature - colorless and light-hued stones are heat-treated to achieve the blue color:

The largest gem topaz deposits are in Brazil and Russia. Other locations include Mexico and the USA (Texas, Colorado, Utah).

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Links:

The Gemstone Topaz: The Mineral & Gemstone Kingdom
Geological Symbols - 50 States List