QUARTZ

Posted by Rasmussen Gems and Jewelry LLC

Quartz is a very common mineral in the earth’s crust (second to feldspar in abundance), and comes in a variety of colors. Seen here is a cluster of quartz crystals. Quartz is silicon dioxide (SiO₂) and is the primary mineral in sand. Quartz has a hardness of seven on the Mohs scale which makes it a good gemstone for all styles of jewelry. In addition, quartz comes in a wide variety of colors. This months’ blog will be devoted to the faceted varieties.

Amethyst is the highest valued form of quartz. Amethyst is purple and the color is produced by the presence of iron in the crystal. In ancient times an amulet of amethyst was thought to prevent drunkenness. Some amethysts will pale in sunlight.

Smoky Quartz has a brown to black coloring, resembling is name “smoky.” The dark coloring is produced by artificial or natural gamma radiation. A misnomer for smoky quartz is smoky topaz, as this is not a topaz in any way, this term should not be used.

The last form to be discussed this month is citrine. This name is derived from the lemon yellow color of the crystal. Most citrines are made by heat tteating amethyst. Like amethyst citrine derives its color from the presence of iron in the crystal.

All forms of quartz are in the trigonal crystal system (hexagonal crystals) having no cleavage, the crystal fractures in a conchoidal fashion. The refractive index is 1.544 to 1.533 with a birefringence of 0.009. Quartz has a specific gravity of 2.65.

For more on this series from John, make sure you check out Tanzanite and Gemstones the Big Four.