Moonstone is one form of orthoclase feldspar.
Orthoclase is a crystal formation of feldspar found commonly in basalt and other igneous rock deposits. While feldspar is the most common rock formation in the world, orthoclase is significantly more scarce. Commercially, it has both industrial and decorative uses. Orthoclase comes in several different forms, but the best-known is probably moonstone.
Orthoclase Composition and Formation
Regular feldspar is an aluminum silicate; orthoclase includes potassium in its chemical composition as well, KAlSi3O8. Orthoclase forms when magma cools relatively quickly either above or below ground. Mineralogists and mining corporations generally mine orthoclase from pockets embedded in granite or pegmatite. It is a relatively durable crystalline mineral, and it cleaves at a perfect right angle.
Where Orthoclase Is Mined
Orthoclase forms several different subminerals dependent on regional geochemical differences. In the Russian Urals and parts of South America, the most common form of orthoclase is microcline, which includes traces of sulfur and is sometimes colored a deep blue-green. Mineralogists classify the best of these microcline orthoclase as the semiprecious stone amazonite. In Madagascar, jewelers and gemologists cut and facet rare transparent orthoclase into jewelry-grade gemstones. Mines from India to Australia and in Brazil produce moonstone. Industrial-grade orthoclase forms in igneous rock worldwide.
Industrial Uses for Orthoclase
Mining companies grind orthoclase that is not distinctive for its color, clarity or other unique qualities into different industrial grades from powder to coarse gravel. Several industries make use of this raw orthoclase as binding agents in porcelain, china and earthenware products, as an ingredient in glass sand and as an abrasive in different commercial cleaning products. It is also common in other ceramic products such as wall and floor tile or dental ceramics, and is a common ingredient in ceramic glaze.
Other Uses for Orthoclase
Orthoclase that is notable for its clarity and beauty and is considered to be gemstone quality. Several different semi-precious gems are forms of orthoclase, including moonstone, beryl and faceted orthoclase. In Madagascar, jewelers cut clear or champagne-colored orthoclase into faceted gemstone to set in jewelry; it looks similar to tourmaline. Gemologists generally classify opalescent orthoclase as moonstone, which jewelers cut into round cabochons, polishing the cut stone to bring out the shimmering colors.
Tags: form orthoclase, igneous rock, Madagascar jewelers, most common, orthoclase into
