Amethyst

Hardness: 7 on the Mohs scale. Color: Shades of purple, from light lilac to deep violet. Luster: Vitreous (glassy). Crystal Structure: Trigonal (hexagonal crystals when fully formed). Cleavage: None (conchoidal fracture). Specific Gravity: 2.65.

Amethyst forms in either hydrothermal veins or in the cavities of igneous rocks (geodes and vugs). Its purple color is attributed to irradiation of iron impurities within the quartz crystal structure, which can happen naturally over geological time scales. Its geological age varies greatly depending on the specific deposit, ranging from millions to billions of years old.

Amethyst is highly valued as a gemstone and is widely used in jewelry (rings, necklaces, earrings). Larger specimens are popular for decorative purposes, such as geode slices and crystal clusters. It is also used in crystal healing and spiritual practices due to its perceived calming and protective properties.

The name 'amethyst' comes from the Greek word 'amethystos,' meaning 'not drunken,' as it was believed to protect its owner from intoxication. Brazil and Uruguay are famous for their large amethyst geodes. The deepest color amethyst, known as 'Siberian' or 'Deep Russian,' is highly prized. Amethyst can fade with prolonged exposure to sunlight and can turn yellow (citrine) or colorless when heated to high temperatures.

In the field, amethyst can be identified by its distinctive purple color, vitreous luster, and hardness (it can scratch glass). It commonly occurs in igneous rocks, particularly in basaltic lava flows where it fills gas cavities. Notable locations include Brazil, Uruguay, Siberia (Russia), Zambia, Bolivia, and parts of the United States (e.g., Arizona, North Carolina). For collectors, look for rich, uniform color and good transparency; larger, well-formed crystals or geode sections are particularly sought after.