mineral
Quartz Geode
Silicon Dioxide (SiO2)
AI-generated identification · may be incorrectHardness: 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
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Physical properties
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
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.
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Metamorphic
Sandstone (with potential mineral staining/concretions)
Arenite (SiO2 based)
sedimentary
Tumbled granite
Granite, a coarse-grained felsic intrusive igneous rock
igneous
Epidote
Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)
metamorphic
Pegmatite with Tourmaline and Quartz
Igneous Pegmatite
igneous
Granite
Granite (Phaneritic intrusive igneous rock)
igneous