Amethyst (variety of Quartz)

Hardness: 7 on Mohs scale. Color: Violet to dark purple, often with color zoning. Luster: Vitreous (glassy). Crystal Structure: Trigonal. Cleavage: None (conchoidal fracture). Specific Gravity: 2.65.

Amethyst forms in hydrothermal veins, geodes, vugs, and cavities in igneous rocks, particularly volcanic basalts. The purple color is due to irradiation of iron impurities within the quartz crystal lattice. Its geological age varies depending on the deposit, but it is found in formations ranging from Precambrian to relatively recent.

Primarily used as a gemstone in jewelry (rings, necklaces, earrings, bracelets like the one shown). Also used for ornamental carvings, interior decoration, and as a collectible mineral specimen. Lower quality amethyst can be used in industrial applications where quartz is utilized, though this is less common due to its value as a gemstone.

The name 'amethyst' comes from the Greek word 'amethustos', meaning 'not drunk', as it was believed to protect against intoxication. Historically, it was revered by royalty and religious figures. Brazil and Uruguay are famous for their large geode formations filled with amethyst crystals. Prolonged exposure to sunlight can sometimes cause amethyst to fade.

In the field, amethyst is identified by its characteristic purple color, hardness (it can scratch glass), and typical crystal habits (prismatic crystals terminating in pyramids, often found lining cavities). It is commonly found in Brazil (especially Rio Grande do Sul), Uruguay, Siberia (Russia), Zambia, Bolivia, and parts of the United States (e.g., Arizona, North Carolina). For collectors, look for vibrant, consistent purple color, good clarity, and well-formed crystals. The image shows polished, spherical beads, which are typical for amethyst used in jewelry.