Quartz

 

<<PREVIOUS   ^   NEXT>>

Quartz, second to feldspar, is one of the most common and varied of all minerals, and is found on every continent of this planet. Some members of the quartz group can exhibit chatoyancy or asterism.  The quartz family is divided into two groups: crystalline and cryptocrystalline. Crystalline quartzes are formed in one distinct crystal and owe their color to a variety of trace elements (also referred to as impurities.) Examples of these transparent, facetable gems include amethyst, smoky topaz and citrine. Cryptocrystalline quartzes are dense formations of infinitesimally small crystals and stained during their formation by solutions containing metallic salts.  Cryptocrystalline quartzes include the ornamental ornamental and rock-like varieties and are classified as either chalcedony or agate.  Chalcedonies are usually stones with one color (owed predominantly to traces of iron oxides) agates with patterns. Some might call cryptocrystalline quartzes "rocks."

 

Rose quartz is an uncommon variety, but still readily available and affordable, ranges from pale pink to deep rose-pink, and is usually slightly cloudy and somewhat brittle. Found in huge formations, little of the material is suitable for faceting. Six legged star rose quartz can also be found in both cabs and spheres. These phenomenon stones display a variety of interlocking stars when illuminated from underneath. Star stones premier source is Sri Lanka. Collector's stones are large with centered, well defined legs. Sources include Madagascar, United States, Brazil, India and Japan. Drusy quartz derives it's name from the Greek drossos, meaning "dew," evolved to the Bohemian druza, and transformed by the Germans to druse. Other gems can display the drusy effect of tiny crytals covering the surface of a gem. Drusy quartzes such as druzy chrysocolla and druzy agates are favorites. A fine drusy has good color, small, fine, even sized crystals without any damage, and a base at least 3mm thick for durability. Lemon quartz is also known as lemon citrine or lemon-lime. Primarily from Brazil, these white rock crystals were irradiated and heated to produce this color. Rutilated quartz is popular with gem carvers although the availability of suitable fine quality rough is hard to come by. This crystalline quartz variety displays needles of rutile fiber inclusions. At their best these stones resemble various patterns of wind-blown straw in a transparent stone. Deep red rutile fibers are the most rare and preferable. Other colors include golden, browns or silver. Smokey quartz is another favorite of gem carvers. Darker stones may be referred to as morion, while vibrant colored are called cairngorm. High altitude mines tend to produce the finer qualities of this variety. Phantom inclusions, the outline of an earlier growth phase within the crystal, are highly desirable and usually appear as a v-shaped color banding. The premier Scottish mines yielding reddish-brown stones have been depleted. Fine Swiss stones, having red and orange flashes, have somewhat replaced them.  Rhinestones were initially colorless rock crystals found in the Rhine River. Tiger's eye is a golden variety of quartz featuring a cat's eye (chatoyancy) due to inclusions of rutile fibers.

 

A common mineral composed of silicon and quartz and colored by minor impurities. Rare in its pure state, this silicon dioxide is referred to as rock crystal. Measures 7 on Mohs scale. More than 40 different tyrpes of minerals have been found as inclusions in quartz varieties.  Sillimanite inclusions are responsible for the stars and stripes in rose quartz from Sri Lanka, rutile inclusions in Brazilian stars.

 

Hand clean included quartz varieties. Others can be cleaned in the ultrasonic.

 

Earth