Smoky Quartz

Hardness: 7 (Mohs scale); Color: Typically smoky gray to brown, can be nearly black; Luster: Vitreous; Crystal Structure: Hexagonal (trigonal system); Cleavage: None; Specific Gravity: 2.65

Smoky Quartz forms in a wide range of geological environments as pegmatites, hydrothermal veins, and igneous and metamorphic rocks. Its formation typically involves the natural irradiation of clear quartz over geological time, which rearranges aluminum impurities within the crystal. This process can occur at various geological ages, often associated with radioactive elements in the surrounding rock.

Smoky Quartz is widely used in jewelry (beads, cabochons, faceted stones) due to its attractive color and durability. It is also used in ornamental carvings, as a decorative stone in interiors, and as a collector's mineral specimen. Historically, it was sometimes used in Scottish jewelry.

Smoky Quartz gets its smoky color from natural irradiation of aluminum within the crystal lattice. The intensity of the color depends on the amount of irradiation and the presence of aluminum impurities. It is often heat-treated to darken its color, but naturally occurring dark smoky quartz is more valuable. It is a popular gemstone and ornamental stone.

In the field, Smoky Quartz can be identified by its distinctive smoky to brownish-gray color, vitreous luster, and its hardness (it scratches glass). It often forms in well-defined hexagonal crystals. Common locations include Brazil, the Swiss Alps, Colorado (USA), Scotland, and Madagascar. For collectors, look for well-formed crystals with good clarity and an even color. Be aware that some dark smoky quartz can be heat-treated clear quartz.