mineral
Quartz geode with druzy quartz
Silica, SiO₂; microcrystalline chalcedony/quartz lining with iron-oxide staining
AI-generated identification · may be incorrectHardness 7 Mohs for quartz; white to gray, translucent chalcedony exterior and sparkling yellow-brown crystalline cavity. Vitreous to sugary luster, hexagonal quartz crystals, no prominent cleavage, specific gravity about 2.65.
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Physical properties
Hardness 7 Mohs for quartz; white to gray, translucent chalcedony exterior and sparkling yellow-brown crystalline cavity. Vitreous to sugary luster, hexagonal quartz crystals, no prominent cleavage, specific gravity about 2.65.
Formation & geological history
Likely a volcanic or sedimentary geode formed when silica-rich groundwater filled a cavity and quartz crystals grew inward; iron oxides caused the brown-gold coloration. Precise age and locality cannot be determined from the image.
Uses & applications
Used as a decorative and collecting specimen; larger polished geodes are popular display pieces, while quartz is important industrially in glass, electronics, abrasives, and engineered stone.
Geological facts
The cavity formed before mineral deposition, commonly from a gas bubble or dissolution void. Druzy refers to a coating of many tiny quartz crystals rather than large individual crystals.
Field identification & locations
Identify by the hollow chalcedony shell and sugary, sparkly quartz lining; a glassy luster and scratch resistance help distinguish it from calcite. Common sources include Brazil, Uruguay, Mexico, Morocco, and the United States.
