mineral

Amethyst Geodes

Silicon Dioxide (Quartz with Iron impurities), SiO2

Hardness: 7 on Mohs scale; Color: Deep purple to violet; Luster: Vitreous (glassy); Crystal Structure: Hexagonal/Trigonal; Specific Gravity: 2.65

Hardness: 7 on Mohs scale
Color: Deep purple to violet
Luster: Vitreous (glassy)

Identified May 23, 2026More mineral →

Identify your own rocks.

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

App Store Google Play

Physical properties

Hardness: 7 on Mohs scale; Color: Deep purple to violet; Luster: Vitreous (glassy); Crystal Structure: Hexagonal/Trigonal; Specific Gravity: 2.65

Formation & geological history

Formed in volcanic cavities or gas bubbles (vesicles) in basalt. As mineral-rich groundwater seeps into these cavities, silica and trace amounts of iron precipitate over millions of years, crystallizing into quartz. The purple color is caused by natural irradiation of the iron impurities.

Uses & applications

Used primarily for interior decoration, luxury collecting, and spiritual/metaphysical purposes. Smaller specimens are used in jewelry and lapidary arts.

Geological facts

The world's largest amethyst geodes often come from the Artigas region of Uruguay. These massive 'cathedrals' can reach heights of over 10 feet and weigh several tons. The purple color of amethyst can fade if exposed to direct sunlight for prolonged periods.

Field identification & locations

Identify in the field by searching for basaltic rock formations with 'bubbles' or rounded nodules; when cracked open, they reveal a hollow interior lined with crystals. Common in Brazil and Uruguay.

Other mineral specimens

See all

Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

sedimentary

Epidote

Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)

metamorphic

Nephrite Jade

Nephrite

Mineral/Rock

Banded Gneiss (River Rock/Pebble)

Gneiss (specifically a banded variety often found as a river rock)

Metamorphic Rock

Green Apatite on Albite

Fluorapatite [Ca5(PO4)3F] on Albite [Na(AlSi3O8)]

mineral

Epidote

Epidote - Ca2(Al2,Fe3+)3(SiO4)3(OH)

mineral