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November-December 2013

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Connoisseur's Choice: Muscovite, Shannon Canyon, Inyo County, California

Rocks are made up of minerals. Some, such as dolomite, are made up of one mineral, but most, such as granite, are made up of two or more minerals. The members of the amphibole, pyroxene, and mica groups are some of the most common and most important rock-forming minerals. And yet the rock-forming minerals as well as most sulfides and sulfosalts are the Rodney Dangerfields of mineral collecting—they get no respect. The rock-forming minerals are usually found in drab, unexciting colors with crystals that are difficult to find in good-quality, collectible specimens. However, there are exceptions, particularly when they occur as the matrix for their more exciting (read colorful) brethren. When I wrote about siderite a few columns back (Pohwat 2012), I compared that species to great character actors, those performers who bring out the very best in the star and the performance in general. Among the minerals that are great “character actors” are pyrite and members of the feldspar and the mica groups, providing aesthetic backgrounds that show off the “stars” to their best advantage. Working with the mineral collection of the Smithsonian, I have developed a particular fondness for muscovite. The texture and earth-tone color of muscovite crystals seem to be a great backdrop for the colorful elbaites and fluorapatites that are collector favorites.

Paul W. Pohwat is the collection manager (minerals) in the Division of Mineralogy at the National Museum of Natural History (Smithsonian Institution).

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