mineral
Quartz Geode
Silicon Dioxide (SiO2) in Geode formation
Hardness: 7 (Mohs scale); Color: Clear to milky white crystals with a tan/brown chalcedony or sedimentary outer shell; Luster: Vitreous; Crystal structure: Hexagonal (trigonal); Specific gravity: 2.65
- Hardness
- 7 (Mohs scale)
- Luster
- Vitreous
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Physical properties
Hardness: 7 (Mohs scale); Color: Clear to milky white crystals with a tan/brown chalcedony or sedimentary outer shell; Luster: Vitreous; Crystal structure: Hexagonal (trigonal); Specific gravity: 2.65
Formation & geological history
Formed as hollow cavities in sedimentary or volcanic rock that are filled through precipitation of minerals from hydrothermal fluids or groundwater over thousands of years.
Uses & applications
Mostly used for decorative purposes, metaphysical collecting, educational specimens, and lapidary art.
Geological facts
Geodes are essentially 'rock bubbles'. While they look like ordinary stones on the outside, their hollow interiors contain beautiful crystal formations. The largest geodes can be big enough for a person to stand inside.
Field identification & locations
Identify by their rounded, potato-like exterior and unusually light weight for their size. Common in desert regions like Morocco, Mexico, and the Midwestern United States.
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Sandstone (with potential mineral staining/concretions)
Arenite (SiO2 based)
sedimentary
Schist
Schist
Metamorphic
Epidote
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metamorphic
Gypsum (variety Selenite or Alabaster)
Calcium sulfate dihydrate (CaSO4·2H2O)
Mineral
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Nephrite
Mineral/Rock
Granite
Granite (Phaneritic intrusive igneous rock)
igneous