mineral

Amethyst on Agate/Basalt Matrix

Silicon Dioxide (SiO2) with iron impurities

Hardness: 7 (Mohs); Color: Pale purple to lilac; Luster: Vitreous (glassy); Crystal structure: Hexagonal/Trigonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Hardness: 7 (Mohs)
Color: Pale purple to lilac
Luster: Vitreous (glassy)

Identified April 11, 2026More mineral →

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Physical properties

Hardness: 7 (Mohs); Color: Pale purple to lilac; Luster: Vitreous (glassy); Crystal structure: Hexagonal/Trigonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Formation & geological history

Formed in hydrothermal veins or cavities (vugs) within volcanic rocks. As mineral-rich water seeps into cavities in basalt, silica precipitates over millions of years, often starting as a layer of agate followed by crystalline quartz.

Uses & applications

Primary use is in jewelry, lapidary arts, and as collectible interior decor. Historically used as an amulet against intoxication and for spiritual/metaphysical practices.

Geological facts

Amethyst is the birthstone for February. Its purple color is caused by gamma irradiation of trivalent iron (Fe3+) in the crystal lattice. Most high-quality amethyst geodes come from Brazil and Uruguay.

Field identification & locations

Identify by its characteristic six-sided crystals with pyramidal terminations and purple hue. It is often found attached to a gray or green host rock (basalt) often with a thin layer of chalcedony or agate in between.

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