mineral

Amethyst cluster/geode half

Amethyst, purple quartz (SiO₂)

AI-generated identification · may be incorrect

Hardness 7 Mohs; purple, vitreous luster, typically transparent to translucent with six-sided quartz crystals and no true cleavage. Purple color comes mainly from iron impurities and irradiation; specific gravity is about 2.65.

Identified August 31, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater deposits quartz crystals in cavities of volcanic rocks, especially basalt; iron impurities create the violet color. Most specimens formed during relatively young volcanic episodes, commonly tens to hundreds of millions of years old.

Uses & applications

Popular as a display specimen, ornamental stone, and inexpensive gemstone; cut amethyst is used in jewelry, while large clusters are collected for décor and mineral education.

Geological facts

The specimen appears to be a cut or broken amethyst-lined cavity, with druzy-to-small quartz crystals and a darker purple central zone. Heat treatment can turn amethyst yellow, producing citrine.

Field identification & locations

Identify by purple quartz crystals, glassy luster, hexagonal forms, and hardness sufficient to scratch ordinary glass; test cautiously because scratching damages the specimen. Common sources include Brazil, Uruguay, Zambia, Mexico, and Namibia.