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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March, 2003

Smoky Quartz

Pale to dark, brown to grey, crystalline quartz is the variety named smoky quartz. The brown and grey colors are created by the altering effect of radiation on the crystal lattice of formerly colorless quartz. The radiation can be natural or provided by man. A larger and larger fraction of the smoky quartz in the marketplace has been laboratory irradiated, although some is still natural. The color is stable and the source of the color cannot be determined with standard gemological labortory equipment. Along with blue topaz, Morganite, aquamarine and Tanzanite, it belongs to the group of gems that you should assume, unless specifically stated otherwise, have been enhanced. (at ACS, smoky quartz is routinely labelled [Gec: E] for this reason, although, some pieces, particularly lighter ones may well be natural.)

Generally available in flawless to near flawless crystals of substantial size cutters and carvers often choose it for exotic cuts or large pieces, so those who enjoy pieces that showcase lapidary skill or innovation often end up with smoky quartz specimens. Smoky quartz sometimes contains rutile inclusions which can be attractive.

The material is widely distributed with the major world sources in Brazil, Madagascar, USA and Switzerland. A very dark brown, nearly black and opaque form has been called "Morion" and also deserving special note is the usually dark material historically mined from mountains in Scotland known as Cairngorm.

As a gem, smoky quartz has all the good attributes of the quartz group: hardness of 7 and good toughness, making it suitable for all types of jewelry, nice luster and, if cut and polished properly, very good brilliance. No extreme heat or chemical sensitivities restrict use or wear or require special care. Although most varieties of quartz (especially amethyst and citrine) have been extensively synthesized, smoky quartz is virtually always of natural origin.


VALUE CONSIDERATIONS

The main reason that synthetic smoky quartz has not made major inroads in the marketplace is that natural (or enhanced natural) material of high quality is abundantly available at very modest prices. In fact, in the purchase of a smoky quartz gem, the cost of the material itself is generally much less than the value added by the artisan who cabs, carves or facets it. There is no reason to accept a smoky quartz gem of an inferior color or clarity. Therefore, the prime value factor for you to consider is artistry of fashioning, with increased carat weights contributing no more than a linear increase in price.
Gemological Properties:

Makeup: Silicon dioxide

Crystal System: Trigonal

Hardness: 7

RI: 1.54 - 1.55

Density: 2.65

Birefringence: .009

Polish Luster: vitreous

Fluorescence: none

Cleavage: none


Stones Currently Available:

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Go to: Homepage -- what's new in faceted gems -- what's new in designer cabochons and gem carvings -- gem of the month -- gem of the month archive -- birthstone of the month -- key to all the codes used on the ACS site -- definitions of terms used on the ACS site -- how to order -- about ACS -- about the ACS cutters -- settings for these gems --faceting information -- purchase UltraTec equipment