Jewelry Lovers

On all continents, in the sand of the seashore, in fissures in the Alps—everywhere quartz is to be found, the most ubiquitous mineral on our earth. The reason for this is that silicon dioxide penetrated throughout the entire magmatic cycle and participated, as quartz, in all stages of rock and mineral formation. In gem quality, with a series of attractive varieties, it emanated only from the pegmatitic, and principally from the hydrothermal, phase. The most valuable specimens are obtained from primary sources, for any quartz lying in gem gravels is washed out during sieving, with the unusable spoil, because of its low specific gravity of 2.65. Its low refractive index of only 1.545 demands as richly faceted a cut as possible, in order to enhance its brilliance by an active play of light.

Water-clear rock crystal handed the euphonious name crystal down to us from the golden age of ancient Greece. The Hellenes believed that the krystallos from the mountains was ice turned to rock, from which the gods had built an earthly dwelling impervious to the heat of the sun. Like the smoky gray, and brown to almost black smoky quartz, the far more valuable variety of amethyst (from the Greek amethyein = to be immune from drunkenness) also gained its lilac to deep violet color not only from allochromatic pigments but also from the age-long incidence of extraterrestrial cosmic radiation. Its color is consequently often unstable and subject to change on heating. The best-known evidence of such thermal color change is the yellow to reddish-brown citrine, which unfortunately is widely offered for sale under the usurped name topaz. In the natural state citrine exists only as a very light yellow gemstone. In the deposits of the north Brazilian state of Bahia amethysts occur in cavities very similar to the alpine fissures. In Minas Gerais they are found in pegmatites in company with smoky quartz. In both the occurrences in Rio Grande do Sul (south Brazil) and near Catalan in adjacent Uruguay they form drusy linings in agate amygdules which have developed in the magmatic rocks. Compared with these classic sources, all others are insignificant. As the birthstone for those born in February, amethyst is linked with durability and steadfastness in love, calling, and friendship. The church has always bestowed on it, even to the present day, a priestly and even hallowed character.

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