Smoky Quartz

Hardness: 7 (Mohs scale); Color: Ranges from light brown/gray to black; Luster: Vitreous (glassy); Crystal Structure: Hexagonal (trigonal system); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Smoky quartz is a variety of quartz that gets its color from natural irradiation of silicon dioxide combined with aluminum impurities. It forms in igneous and metamorphic rocks, often within hydrothermal veins, pegmatites, and high-temperature intrusive rocks. Its formation is typically associated with radioactive elements in the surrounding rock, which cause structural defects in the crystal lattice that lead to its characteristic smoky color.

Predominantly used in jewelry as beads, cabochons, and faceted stones. Also used as ornamental stones for carvings and decorative objects. It has also been historically used in optical instruments due to its clarity and durability. In metaphysical beliefs, it is often associated with grounding and protection.

Smoky quartz can sometimes contain rutile needles, creating a 'rutilated smoky quartz'. The intensity of the color can vary greatly, from a light smoky hue to an opaque black, sometimes called Morion. Unlike heat-treated amethyst (which can also become yellowish or brownish), natural smoky quartz achieves its color through radiation. Many pieces of smoky quartz in the market are irradiated clear quartz to enhance their color.

In the field, smoky quartz can be identified by its characteristic smoky to black color, vitreous luster, and hardness (it will scratch glass). It often forms in well-defined hexagonal crystal prisms, though the beads in the image are polished and rounded. It is commonly found in Brazil, the Swiss Alps, Scotland (where it is known as Cairngorm), the Pikes Peak region of Colorado in the USA, and Madagascar. Natural radiation sources can turn clear quartz smoky over geological timescales.