Smoky Quartz

Hardness: 7 on Mohs scale. Color: Translucent grayish-brown to black. Luster: Vitreous (glassy). Crystal Structure: Hexagonal (trigonal) system. Often occurs in prismatic crystals with pyramidal terminations, or as massive forms. Cleavage: None (conchoidal fracture). Specific Gravity: 2.65.

Smoky quartz forms in igneous and metamorphic rocks, often in hydrothermal veins and pegmatites. Its distinct smoky color is caused by natural irradiation of silicon dioxide, which converts trace amounts of aluminum within the crystal lattice into color centers. The geological age varies depending on the specific deposit. It is found in environments where exposure to natural radiation is present during its formation or subsequently.

Commonly used in jewelry (cut into facets, cabochons, or beads), ornamental carvings, and as a popular mineral specimen for collectors. Historically, it was used for scrying and as sunglasses in China due to its ability to reduce glare.

Smoky quartz is a variety of quartz, which is the second most abundant mineral in the Earth's continental crust. Unlike many other colored gemstones, the color of smoky quartz is generally stable to light and heat, although excessive heat can lighten its color. It is sometimes created artificially by irradiating clear quartz.

In the field, smoky quartz can be identified by its characteristic smoky color, glassy luster, hardness (it will scratch glass), and conchoidal fracture. It often forms well-defined hexagonal prisms. Commonly found in Brazil, Switzerland (especially the Alps, where large crystals have been found), the United States (e.g., Colorado, Arkansas), Myanmar, Russia, Scotland (where it is known as Cairngorm), and Ukraine. Tips for collectors include looking for well-formed crystals in pegmatites and hydrothermal veins, and differentiating it from black tourmaline (schorl), which has a columnar habit and often vertical striations.