Reference work entry
Celestite is a gem-quality lapis lazuli mineral. It is composed of (Sr, Ba)SO 4 and often contains Pb, Ca, and Fe. Gem-grade lapis lazuli is seldom mono-crystalline but is often in the form of stalactites or nodular aggregates. Celestite can be blue, blue-green, green, yellowish green or orange, and the blue stones are most valuable. The main mining areas include the United States, Canada, Namibia, Mexico, Britain, France and Italy (Fig. 21).
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