Amethyst

Hardness: 7 on Mohs scale; Color: Purple (various shades from pale lilac to deep violet); Luster: Vitreous (glassy); Crystal Structure: Hexagonal (rhombohedral); Cleavage: None; Specific Gravity: 2.65

Amethyst is a variety of quartz that forms in hydrothermal veins and cavities within igneous rocks (often basalt). The purple color is due to irradiation of iron impurities within the quartz crystal during its formation. It is typically found in geodes or drusy coatings lining cavities, forming over millions of years.

Amethyst is primarily used as a gemstone in jewelry, including rings, necklaces, and earrings. Larger specimens are popular as decorative pieces, for crystal healing practices, and as collector's items. Due to its hardness, it can also be used for some industrial abrasives, though this is less common than other quartz varieties.

The word "amethyst" comes from the Greek word "amethystos," meaning "not intoxicated," as ancient Greeks believed it could prevent drunkenness. It was highly valued by ancient Egyptians, Romans, and Greeks, and was often worn by royalty and religious figures. The largest amethyst geode in the world is the 'Empress of Uruguay'.

In the field, amethyst can be identified by its distinctive purple color, glassy luster, and typical hexagonal crystal habit, often found in crystal-lined vugs or geodes within volcanic rocks. It will scratch glass but cannot be scratched by a steel knife. Common locations include Brazil (especially Minas Gerais), Uruguay, Siberia (Russia), Zambia, Canada, and various localities in the United States.