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About Minerals

Garnet

As it was in ancient times garnet is January's birthstone. In those years all red stones were collectively called carbuncle, but through the centuries classifications proceeded to distinguish one from the other. Now by analysis of chemical and structural composition the word garnet refers to a group of six isometric crystal forms and their numerous colored varieties. Garnets occur in all colors but blue. They are found in a variety of rock types but crystallize most often in metamorphic rocks—especially mica schists, and gneisses. Because they are so hard they are impervious to most types of chemical weathering, and are found abundantly in areas near weathering rocks rich in garnets. Since they are heavy they tend to settle down through detritus and concentrate at the bottom of the “pile”. The crystal forms range from 12 sided dodecahedron to even an 84 sided crystal. Through most garnets are found as distinct crystals they can be found as rounded grains, granular masses and sometimes as “snowball garnets”.

If the garnet is of excellent color and clarity all forms of garnet (except for uvaroite which is tiny drusy crystals). Deep colored garnets are cut as cabs and called carbuncles. Pyrope and rhodolite garnets are generally flawless and make beautiful gemstones, while almandine stones are likely to be flawed and contain inclusions. Garnets containing closely packed inclusions of oriented rutile are called star garnets when they have been cut to enhance the brilliance of the inclusions. The most valuable gem garnet is the green variety of andradite called demantoid, which rivals the clarity and fire of a diamond.

Garnet has been used throughout history as a decorative stone as well as a metaphysical tool and an astrological charm but is also used widely as an abrasive and has been for thousands of years for finishing hardwood projects and grinding softer stones and glass.

Reference: program prepared for a meeting of the Panorama Club in 1996 by Leonard Neyens, Jr.