mineral

Quartz Geode

Silicon Dioxide (SiO2)

Hardness: 7 on Mohs scale; Color: Clear to white internal crystals with a dark grey or brown outer rind; Luster: Vitreous (glassy) crystals; Crystal Structure: Hexagonal; Cleavage: None; Specific Gravity: 2.65

Hardness: 7 on Mohs scale
Luster: Vitreous (glassy) crystals

Identified May 15, 2026More mineral →

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Physical properties

Formation & geological history

Formed as hollow cavities in volcanic ash or sedimentary rock which are later filled by mineral-rich hydrothermal fluids. The crystals grow inward over thousands of years.

Uses & applications

Primarily used as decorative display pieces, in lapidary work, jewelry, and for education in geological collections.

Geological facts

The word geode comes from the Greek word 'Geoides' meaning earth-like. No two geodes are exactly alike on the inside, often containing a sequence of mineral layers such as chalcedony and macrocrystalline quartz.

Field identification & locations

Identify by looking for a rounded, nodular exterior that feels lighter than a solid rock of the same size. Commonly found in deserts, volcanic ash beds, and limestone regions. Morocco and Brazil are famous global sources.