mineral

Amethyst Geode

Amethyst (SiO2) - Silicon Dioxide with Trace Iron Impurities

AI-generated identification · may be incorrect

Hardness: 7 Mohs; Color: Deep purple to pale violet; Luster: Vitreous; Crystal Structure: Hexagonal (Trigonal); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 Mohs
Color: Deep purple to pale violet
Luster: Vitreous

Identified May 23, 2026More mineral →

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Physical properties

Hardness: 7 Mohs; Color: Deep purple to pale violet; Luster: Vitreous; Crystal Structure: Hexagonal (Trigonal); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Formation & geological history

Formed when silica-rich hydrothermal fluids precipitate inside volcanic gas bubbles or sedimentary cavities. As the fluid cools and reacts with iron, amethyst crystals grow inward. Most of these giant geodes originated in the Parana Basin (Brazil/Uruguay) roughly 130 million years ago.

Uses & applications

Primarily used for large-scale interior décor, crystal healing collections, feng shui, and museum displays. Smaller specimens are used in jewelry and lapidary art.

Geological facts

The purple color is the result of gamma irradiation and trace amounts of iron within the crystal lattice. If heated, amethyst will turn yellow-orange, becoming heat-treated citrine.

Field identification & locations

Identify by the distinct purple hexagonal crystal points growing toward a hollow center. Large basalt-backed geodes are typically found in South America. In the field, look for roundish boulders (vugs) with a rocky, drab exterior.