Amethyst Geode

Physical Properties

Hardness: 7 on Mohs scale; Color: Purple/violet crystalline center with a white/grey chalcedony band and dark basaltic crust; Luster: Vitreous (glassy); Crystal Structure: Hexagonal; Cleavage: None/Conchoidal fracture; Specific Gravity: 2.65.

Formation & Geological History

Formed in hollow cavities (vugs) within volcanic rock (basalt) or sedimentary formations. Silica-rich hydrothermal fluids seeped into the cavities, slowly precipitating crystals over millions of years. This specimen likely dates from the Cretaceous period.

Uses & Applications

Used primarily for jewelry, decorative home decor, metaphysical/healing practices, and as educational geological specimens for collectors.

Geological Facts

The purple color is caused by the irradiation of iron impurities within the quartz structure. Significant deposits are found in the basalt flows of the Paraná Basin in Brazil and Uruguay.

Field Identification & Locations

Identify in the field by looking for 'thunderegg' or potato-like nodules that feel lighter than solid basalt. They are commonly found in volcanic regions. To verify, a sample must be cracked open to reveal the crystalline interior.

Identified on: 4/29/2026

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