Sedimentary/Igneous (depending on host rock)

Geode with Quartz Crystals

SiO2 (Silicon Dioxide) in a geode formation

AI-generated identification · may be incorrect

Hardness: 7 (Quartz); Color: Clear, white, grey; Luster: Vitreous (glassy) inside, dull outside; Crystal structure: Trigonal (Quartz).

Hardness: 7 (Quartz)
Color: Clear, white, grey
Luster: Vitreous (glassy) inside, dull outside

Identified August 25, 2026More sedimentary/igneous (depending on host rock) →

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Physical properties

Hardness: 7 (Quartz); Color: Clear, white, grey; Luster: Vitreous (glassy) inside, dull outside; Crystal structure: Trigonal (Quartz).

Formation & geological history

Formed in cavities in sedimentary or igneous rocks, where mineral-rich water deposits layers of silica (often chalcedony or agate) and inward-growing crystals over thousands to millions of years.

Uses & applications

Commonly collected for aesthetic value, used in jewelry making, or as decorative display pieces.

Geological facts

Geodes are often hollow, but some are completely filled with crystals (called nodules). The word 'geode' comes from the Greek word 'geodes', meaning 'earthlike'.

Field identification & locations

Identified by a rough, relatively unremarkable exterior and a hollow interior lined with crystals. Often found in limestone deposits or volcanic ash beds.