mineral

Quartz geode

Silica geode lined with microcrystalline quartz (SiO₂), possibly chalcedony

AI-generated identification · may be incorrect

Hardness 7 (quartz), vitreous to dull luster, white-gray exterior with sparkling drusy crystals and a hollow cavity; quartz has a trigonal crystal structure and no cleavage. The dark interior may reflect lighting or minor iron/manganese staining.

Identified August 24, 2026More mineral →

Explore Quartz geode 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 gas bubbles or cavities in volcanic basalt are later filled by silica-rich groundwater; successive mineral layers crystallize inward, commonly during the Cenozoic or older volcanic episodes.

Uses & applications

Used as a decorative and collectible specimen; larger, colorful geodes are used in lapidary displays and jewelry. This example appears natural and cut or broken open, rather than fully polished.

Geological facts

The cavity is called a vug, and tiny quartz crystals lining it are termed drusy. Quartz geodes can also contain amethyst, calcite, or agate, though obvious purple amethyst is not visible here.

Field identification & locations

Identify by the hard, rough chalcedony/quartz rind and crystalline lining; it should scratch glass but not be scratched by a steel knife. Common sources include Brazil, Uruguay, Mexico, Morocco, and the western United States.