mineral
Quartz geode/drusy quartz
Quartz, silicon dioxide (SiO₂), likely chalcedony-lined geode
AI-generated identification · may be incorrectWhite to gray, translucent quartz crystals with a vitreous to sparkling drusy luster in a tan, porous host. Mohs hardness 7; hexagonal crystal structure, no cleavage, conchoidal fracture, and specific gravity about 2.65.
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Physical properties
White to gray, translucent quartz crystals with a vitreous to sparkling drusy luster in a tan, porous host. Mohs hardness 7; hexagonal crystal structure, no cleavage, conchoidal fracture, and specific gravity about 2.65.
Formation & geological history
Forms when silica-rich groundwater deposits chalcedony and quartz crystals inside a cavity, commonly in volcanic vesicles or sedimentary concretions. The specimen’s exact geological age cannot be determined from the image; geodes range from young to Paleozoic and younger deposits.
Uses & applications
Used as a decorative, lapidary, and mineral-collecting specimen; larger polished geodes are popular home décor. Quartz is also important industrially in glass, electronics, abrasives, and construction aggregates.
Geological facts
The sparkling surface is drusy quartz—many tiny crystals coating the cavity. Quartz commonly displays strong resistance to weathering and can scratch ordinary glass.
Field identification & locations
Identify by its glassy sparkle, hardness, lack of cleavage, and crystals lining an interior cavity; a steel file should not readily scratch it. Common sources include Brazil, Uruguay, Mexico, Morocco, and the western United States.
