Jewelry Lovers

The collective name garnet embraces a large mineral group whose members each have their own individual names corresponding to their appearance. This family provides a good example of the fact that though the structure of a mineral determines its external form (garnets crystallize throughout in the cubic system), it is the chemical composition which is fundamental to the color, in that one important component may replace another and in this way produce varieties completely different from one another.

Pyrope, endowed with its glowing red color by allochromatic chromium, is a magnesium-alumina garnet, whose occurrences are confined to Bohemia, South Africa, and Arizona As a typical representative of basic mineral development, it is formed along with diamond, so that it often provides gem prospectors with a pointer to deeper lying diamond grounds Bohemian pyropes were much coveted by our forefathers, and beautiful specimens of them decorated the crown jewels of the Bohemian King Wenceslas; for many centuries, because of their slight similarity of color, they were taken for rubies. The always moderating influence of magnesium here ensures the golden mean of properties: the refractive index of pyrope, whose name is borrowed from the Greek word for fire, is 1.75, its specific gravity 3.75.

Almandine is a brownish red to reddish violet iron-alumina garnet, colored by the idiochromatic element iron. Wherever iron enters into the chemical composition of a gemstone it deepens the color and heightens the properties. So almandine possesses a higher refractive index (1.795) and greater specific gravity (4.1) than pyrope. Almandines result from various rock-forming processes. They are minerals of igneous and contact-metamorphic rocks as well as of crystalline schists, which explains their wide distribution in almost all important gemstone localities. From the town of Alabanda in Asia Minor Pliny derived the description carbunculus alabandicus, which gave almandine its name in the familiar company of the carbuncle stones.

Rhodolite is seen as the link member between pyrope and almandine, with which it forms the red garnet series of the pyrandines. Magnesium and iron are here balanced and bestow on it the, at present, particularly popular rose-red color and strong luster. The most outstanding rhodolites come from North Carolina, and from Africa’s new treasure chest, Tanzania.

In spessartite, a manganese-alumina garnet another surprising member joins the family; its hot orange hue embodies the molten fires of the earth’s core, and, when large and clear and cut with many facets, it is one of the most outstanding garnets. The combination of manganese with alumina and silica in its composition accounts for its extraordinarily gorgeous idiochromatic color; also for the strongly increased values of light refraction (1.8), thus bestowing a dazzling brilliance on this glowing gemstone, and for the specific gravity (4.16), which considerably reduces the labor of separating it out from alluvial deposits. In Tanzania spessartite is recovered, with rhodolite, from a hornblende-gneiss, and in Ceylon, accompanied by essonite, from the gem gravels.

The most unusual among the garnets is certainly the glistening green demantoid, which consists of the combination. The rare pigment chromium, as well as an amazingly high refractive index (1.89) and its fire (0.057) exceeding that of diamond, wreathes demantoid in its aureole of coruscating beauty, which might seriously rival even emerald were demantoid not softer and so extremely rare that it is found in only two places, the Congo and the Urals.

The appearance of grossularite, a calcium-alumina garnet, is less splendid but at the same time more varied. The most familiar is the brown to dull red-brown essonite (cinnamon stone) from Ceylon and Brazil, to which has recently been added a clear sparkling copper-gold variety from Quebec in Canada and a light green from Tanzania. Both the brothers from the Transvaal—the gooseberry green massive grossularite dotted with black spots and the raspberry red massive grossularite—are opaque.

The origin of the name “garnet,” from Latin granatus = seed, refers to the appearance of very tiny crystals, usually unsuited for gem purposes, thickly sprinkled in matrix, as they occur in the most striking deposit in mica schists beneath the Manhattan area of New York city. Garnet is regarded as the protector of the crusader from wounds and poison, and as the birthstone for those born in January, symbolizing fidelity, friendship, and constancy.

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