mineral

Agate and Amethyst (Quartz variants)

Silicon Dioxide (SiO2) - Microcrystalline Quartz and Crystalline Quartz

Hardness: 7 on Mohs scale. Color: Brown/white banded (Agate), Purple with white bands (Amethyst/Chevron Amethyst). Luster: Vitreous to waxy. Structure: Trigonal/Hexagonal. Cleavage: None (Conchoidal fracture). Specific Gravity: 2.65.

Hardness: 7 on Mohs scale
Luster: Vitreous to waxy

Identified March 15, 2026More mineral →

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Physical properties

Formation & geological history

Formed as secondary minerals in volcanic rock cavities (geodes) or sedimentary layers. Silica-rich fluids precipitate over time; the purple color in Amethyst comes from iron impurities and natural irradiation, while Agate banding occurs due to rhythmic crystallization.

Uses & applications

Used widely in lapidary arts, jewelry (cabochons and beads), ornamental decor, and as 'healing crystals' in metaphysical markets. Industrial uses include precision mortars and pestles and burnishing tools.

Geological facts

Agates get their name from the Achates River in Sicily where they were first found. Amethyst was once considered a 'Cardinal Gem' equal in value to Diamond and Ruby until large deposits were found in Brazil.

Field identification & locations

Identify in the field by their hardness (cannot be scratched by a steel knife) and waxy luster when broken. Common in Brazil, Uruguay, India, and the Lake Superior region in the USA. Collectors look for unique banding patterns or deep purple saturation.

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