mineral
Quartz Geode
Crystalline Quartz (SiO2) within a sedimentary/igneous host
Hardness: 7 (Mohs scale), Color: Clear to white crystals in a grey/brown rind, Luster: Vitreous (glassy) crystals, Crystal structure: Trigonal/Hexagonal, Specific Gravity: 2.65
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Physical properties
Hardness: 7 (Mohs scale), Color: Clear to white crystals in a grey/brown rind, Luster: Vitreous (glassy) crystals, Crystal structure: Trigonal/Hexagonal, Specific Gravity: 2.65
Formation & geological history
Formed when gas bubbles in volcanic rock or cavities in sedimentary rock are filled by hydrothermal fluids over thousands of years, allowing quartz crystals to grow inward from the hollow center.
Uses & applications
Primarily used for home decor, educational displays, geological collecting, and metaphysical purposes.
Geological facts
The name 'geode' comes from the Greek word 'Geoides' meaning 'earth-like'. No two geodes are exactly alike, and they often look like ordinary, bumpy rocks until they are cracked open.
Field identification & locations
Identified in the field by their rounded or potato-like shape and unusually light weight for their size. Prolific sources include Brazil, Mexico, and the Midwestern United States (Keokuk region).
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