Quartz is by far the most versatile of any of the gem families. Among its members, it includes more variety and a larger number of gems than any of the other three mineral families put together. In the gem trade, the old saying “when in doubt, say quartz,” still holds true. Quartz minerals are relatively inexpensive gems that offer a wide range of pleasing color alternatives in both transparent and nontransparent varieties, from translucent to opaque. They are a wonderful choice for affordable jewelry.
Quartz is one of the most common minerals on earth. The most famous variety of quartz is the amethyst. Quartz comes in transparent and opaque colors and also comes colorless. Smoky quartz rates a 7 on the hardness scale. It is a tan to dark brown type of transparent quartz, and is sometimes incorrectly called smoky topaz or citrine. While it is not known for certain, it is believed that the color of smoky quartz comes from exposure to low grade radiation from uranium and thorium in rocks in the ground. In fact, smoky quartz can be made in a laboratory by exposing clear rock crystal to low-grade radiation.
Today, most of the smoky quartz on the market has been color enhanced or modified in some way. One indication of heat treatment is an excessive uniformity of color, particularly in dark specimens. In crystals, naturally smoky quartz is brown to the base, while irradiated specimens will show some white color. Smoky quartz is very plentiful and is popular for use in large sizes for beautiful brooches, large dinner rings and so forth.
When heated to temperatures of 300-400 degrees, smoky quartz will pale and lose its color, gradually becoming once again clear. When a smoky quartz is almost black in color, it is known as “morion,” according to Simon and Schuster’s Guide to Rocks and Minerals.
Quartz occurs in many igneous and metamorphic rocks, particularly in granite and gneiss. It also often occurs in granitic rocks that have small amounts of radioactivity. Quartz can be found in Australia, Sri Lanka, Brazil, Canada, France, Germany, Bavaria, India, Spain, Scotland, Switzerland, Madagascar, Russia, and the US (in Maine, Colorado and New Hampshire). The earth forms the quartz we know when natural quartz containing small amounts of aluminum is irradiated by exposure to natural radioactivity. Outstanding quality smoky quartz has been obtained from hot, hydrothermal veins in the Malagasy Republic and Brazil. In fact, crystals weighing up to 650 pounds have been found in Brazil. In the United States, Colorado produces some of the best smoky quartz.
Quartz can easily be scratched or chipped so it is important to be careful not to wear it when you might be engaging in an activity that could harm the stone. The best way to clean your quartz is with a plain water and soap, using a soft brush and then a soft polishing cloth. Do not soak your quartz, and do not leave it in direct sunlight as its color may fade. Also be careful not to expose it to intense heat as this too might cause the color to fade.