sedimentary

Quartz Geode

Silicon Dioxide (SiO2)

Hardness: 7 (Mohs scale); Color: White to translucent crystals with a brownish/tan exterior; Luster: Vitreous (glassy) inside, dull outside; Crystal Structure: Trigonal/Hexagonal; Cleavage: None/Conchoidal.

Hardness: 7 (Mohs scale)
Color: White to translucent crystals with a brownish/tan exterior
Luster: Vitreous (glassy) inside, dull outside

Identified April 11, 2026More sedimentary →

Identify your own rocks.

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

App Store Google Play

Physical properties

Formation & geological history

Formed as secondary structures within sedimentary rocks (like limestone) or volcanic rocks. Cavities created by bubbles or organic matter are later filled by mineral-rich hydrothermal fluids that precipitate crystals over millions of years.

Uses & applications

Primarily used as decorative display specimens, for geological education, in jewelry making (slices), and highly valued by metaphysical collectors.

Geological facts

Geodes are essentially 'vug' rocks with a hollow interior. The word 'geode' comes from the Greek word 'geoides', meaning 'earth-like'. One of the most famous geode deposits is the Keokuk Geode beds in Iowa, USA.

Field identification & locations

Identify in the field by looking for rounded, lumpy nodules that feel lighter than typical rocks of that size. They often have a cauliflower-like exterior texture. Found in areas with limestone or basalt outcrops.