Gem of the Month

Each month this section will feature either a topic of interest to gem lovers or one special gemstone with background on the material and its value.

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Amethyst

February, 2000

Crystalline quartz in colors ranging from pale lilac to deep reddish purple and ranging from transparent to translucent is known as amethyst. Siberian mines once produced the world's finest stones with particularly rich purple color that glowed with reddish and/or bluish highlights. Today the term Siberian no longer is a place designation, as the mines are long since worked out, but instead is used a a "grade" term, implying colors similar to the original stones from Siberia. Today's major sources are Brazil, Bolivia and Uruguay in South America and Zambia in Africa. Brazilian stones can be found in huge sizes, but generally are moderate in color and often suffer from color-banding, which sometimes is visible despite efforts of the cutter to minimize it. Many amethyst lovers prefer the usually smaller, but more richly colored stones coming from Zambia, and more recently from Uruguay. Very light amethyst, which once was considered low grade, has gained a recent boost in popularity by intensive marketing on TV shopping programs and the clever marketing strategy of calling it "Rose d' France". To my mind these light stones have their greatest appeal when given fancy and unusual cuts, where the artistry of cutting is more on display than the material itself. At hardness 7 and with no particular warnings on care necessary, amethyst makes a fine jewelry gem for all purposes. Lower grades of material are cabbed, carved, and made into a great variety of beads and other ornamental objects.

Value

Value per carat in amethyst, unlike many gems, doesn't rise exponentially with weight, as it is readily available in large sizes, but depends almost entirely on color. The "Siberian" deep purple with red and blue flash commands the highest prices. The stone is plentiful in the marketplace, so there is no reason to pay top dollar for stones with visible inclusions or inferior cutting.

Gemological Data:

Makeup: Silicon Dioxide

Luster: Vitreous

Hardness: 7

Crystal structure: Trigonal

Fracture: Conchoidal

Cleavage: none

Density: 2.65

RI: 1.54 - 1.55

Birefringence: 0.009

Pleiochroism: weak to moderate purple and reddish purple

Dispersion: .013

Stones Currently Available:

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