mineral

Amethyst

Silicon Dioxide with trace Iron (SiO2)

Hardness: 7 on Mohs scale; Color: Purple to deep violet (often zoned); Luster: Vitreous (glassy); Crystal structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Hardness: 7 on Mohs scale
Color: Purple to deep violet (often zoned)
Luster: Vitreous (glassy)

Identified March 28, 2026More mineral →

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Physical properties

Hardness: 7 on Mohs scale; Color: Purple to deep violet (often zoned); Luster: Vitreous (glassy); Crystal structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Formation & geological history

Formed in hydrothermal veins or volcanic geodes. The purple color is caused by irradiation of trivalent iron (Fe3+) within the quartz lattice. Ages range from millions to billions of years depending on source region.

Uses & applications

Primary use in jewelry (gemstone), metaphysical/spiritual collecting, and interior decoration as cathedral geodes.

Geological facts

Until the 18th century, amethyst was considered one of the 'cardinal' gemstones, valued as highly as diamonds and rubies. It can fade if left in direct sunlight for long periods due to changes in the oxidation state of the iron impurities.

Field identification & locations

Identify in the field by its purple hue, hexagonal prism crystal habits, and ability to scratch glass. Commonly found in Brazil, Uruguay, Zambia, and South Korea. Look for its presence in cavities of igneous rocks.