mineral

Amethyst Geode

Silicon Dioxide (SiO2) with trace Iron (Fe3+) impurities

Hardness: 7 on Mohs scale. Color: Pale violet to deep purple. Luster: Vitreous (glassy). Crystal Structure: Hexagonal (trigonal) prisms. Cleavage: None (conchoidal fracture). Specific Gravity: 2.65.

Hardness: 7 on Mohs scale
Color: Pale violet to deep purple
Luster: Vitreous (glassy)

Identified March 14, 2026More mineral →

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Physical properties

Hardness: 7 on Mohs scale. Color: Pale violet to deep purple. Luster: Vitreous (glassy). Crystal Structure: Hexagonal (trigonal) prisms. Cleavage: None (conchoidal fracture). Specific Gravity: 2.65.

Formation & geological history

Formed in hollow cavities (vugs) within igneous rocks, particularly basaltic volcanic flows. Hydrothermal fluids rich in silica and iron trace elements seep into these gas bubbles; as the fluids cool, crystals grow inward. Many commercial specimens date back to the Cretaceous period.

Uses & applications

Primary use in jewelry (birthstone for February), decorative home decor, lapidary arts, and mineral collecting. In industry, quartz is used for its piezoelectric properties, though amethyst is mostly valued for aesthetics.

Geological facts

Amethyst's name comes from the Greek 'amethystos', meaning 'not drunk', as ancient Greeks believed it prevented intoxication. The purple color is caused by irradiation of iron impurities in the crystal lattice. If heated to high temperatures, it will turn yellow and become citrine.

Field identification & locations

Identify by its characteristic purple terminal crystal points inside a hard, rocky outer rind. Common locations include Brazil (Rio Grande do Sul) and Uruguay. In the field, look for rounded, heavy nodules that sound hollow when tapped, often found in weathered volcanic soil.

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