mineral

Amethyst cluster

Amethyst, purple quartz (SiO₂)

AI-generated identification · may be incorrect

Typically purple, vitreous luster, hexagonal quartz crystals, no cleavage, conchoidal fracture, Mohs hardness 7, and specific gravity about 2.65. The specimen appears to be a natural crystal cluster, possibly on a pale quartz or host-rock base.

Identified September 16, 2026More mineral →

Explore Amethyst cluster 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 when iron-bearing silica-rich groundwater fills cavities in volcanic rocks; irradiation and heat produce the purple color. Most deposits formed in Mesozoic–Cenozoic volcanic environments, especially in Brazil, Uruguay, Zambia, and Mexico.

Uses & applications

Used as a lapidary and jewelry stone, ornamental specimen, and decorative geode material; it has no major industrial use beyond quartz-related applications.

Geological facts

Amethyst is the purple variety of quartz, with color ranging from lilac to deep violet; heating can turn it yellow or orange, producing citrine-like material.

Field identification & locations

Identify it by purple transparent-to-translucent quartz crystals, glassy luster, hardness 7, and lack of cleavage; it will scratch glass but not be scratched by a steel knife. Common sources include basalt cavities in Brazil and Uruguay.