mineral

Amethyst on Agate Geode Fragment

Silicon Dioxide (SiO2) with iron impurities

Hardness: 7 (Mohs); Color: Pale lavender to deep violet on a white/gray base; Luster: Vitreous (glassy); Crystal Structure: Hexagonal (trigonal); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.

Hardness: 7 (Mohs)
Color: Pale lavender to deep violet on a white/gray base
Luster: Vitreous (glassy)

Identified July 20, 2026More mineral →

Explore Amethyst on Agate Geode Fragment in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Forms in hollow cavities (geodes) within volcanic rocks when hydrothermal fluids rich in silica and iron precipitate crystals over millions of years. Common in basalt flows.

Uses & applications

Primarily used for decorative purposes, jewelry, metaphysical practices, and as a popular specimen for mineral collectors.

Geological facts

The purple color in amethyst is caused by irradiation of trivalent iron impurities (Fe3+) in the quartz structure. It was once considered as valuable as diamonds until large deposits were found in Brazil in the 19th century.

Field identification & locations

Identifiable by its purple crystalline habit and association with a chalcedony or agate rind. Often found in South America (Brazil, Uruguay) and parts of North America (Lake Superior region, Arizona).

Other mineral specimens

See all

Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

sedimentary

Schist

Metamorphic

Sandstone with Mineral Veining or Crust

Sedimentary Sandstone (mostly SiO2 with Fe2O3 tinting)

sedimentary

Potassium Feldspar (Orthoclase)

Orthoclase (KAlSi3O8)

mineral

Gypsum (variety Selenite or Alabaster)

Calcium sulfate dihydrate (CaSO4·2H2O)

Mineral

Nephrite Jade

Nephrite

Mineral/Rock