mineral

Quartz Geode

Silicon Dioxide (SiO2)

Hardness: 7 on Mohs scale; Color: Clear to white internal crystals with a grey or brown chalcedony/rock outer rind; Luster: Vitreous (glassy) inside, dull outside; Crystal Structure: Hexagonal/Trigonal; Cleavage: None/Conchoidal fracture.

Hardness: 7 on Mohs scale
Luster: Vitreous (glassy) inside, dull outside

Identified June 23, 2026More mineral →

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Physical properties

Formation & geological history

Formed in cavities within volcanic or sedimentary rocks. Gas bubbles in lava or voids in limestone are filled by mineral-rich hydrothermal fluids over thousands of years, typically during the Cenozoic era.

Uses & applications

Primary uses are for decorative display, crystal healing practices, geological education, and mineral collecting. Large, high-quality geodes are often sliced for high-end home decor.

Geological facts

The word 'Geode' comes from the Greek word 'Geoides', meaning 'earth-like'. Despite looking like ordinary round rocks on the outside, their hollow interiors can contain a variety of crystals including amethyst, citrine, and celestite.

Field identification & locations

Identify in the field by looking for rounded, bumpy, or lumpy nodules that feel lighter than they look (indicating a hollow center). Common in desert regions of the US, Mexico, and Brazil. Collectors should look for thin outer walls and large, well-defined internal crystals.