mineral

Amethyst (Geode)

Silicon Dioxide with Iron impurities (SiO2)

Hardness: 7 on Mohs scale; Color: Deep purple to lavender; Luster: Vitreous (glass-like); Crystal Structure: Hexagonal (trigonal); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 on Mohs scale
Color: Deep purple to lavender
Luster: Vitreous (glass-like)

Identified March 18, 2026More mineral →

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Physical properties

Hardness: 7 on Mohs scale; Color: Deep purple to lavender; Luster: Vitreous (glass-like); Crystal Structure: Hexagonal (trigonal); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Formation & geological history

Formed within volcanic rock cavities (geodes) when silica-rich hydrothermal fluids seep into gas bubbles (vesicles). Over millions of years, crystals grow inward. Most commercial specimens from South America date back to the Cretaceous period (approx. 130 million years ago).

Uses & applications

Primary use in jewelry, lapidary arts, and as high-end interior decor or collector specimens. Also widely used in spiritual and alternative healing practices.

Geological facts

The purple color comes from irradiation of trivalent iron impurities. If heated to high temperatures (approx. 400-500°C), it often turns yellow or orange and is sold as 'heated citrine.'

Field identification & locations

Identify by its distinct purple hexagonal crystal terminations and host rock (often green celadonite or gray basalt). Commonly found in Rio Grande do Sul, Brazil, and Artigas, Uruguay. Collectors look for deep 'grape' saturation and large crystal points.

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