mineral
Druzy quartz in agate/geode
Quartz (SiO₂), microcrystalline chalcedony host
AI-generated identification · may be incorrectWhite, sugary microcrystals with vitreous-to-sparkly luster lining cavities and thin translucent chalcedony bands. Quartz hardness is 7 Mohs, lacks cleavage, has hexagonal crystal structure, and specific gravity about 2.65; visible brown areas are likely iron-oxide staining or matrix.
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Physical properties
White, sugary microcrystals with vitreous-to-sparkly luster lining cavities and thin translucent chalcedony bands. Quartz hardness is 7 Mohs, lacks cleavage, has hexagonal crystal structure, and specific gravity about 2.65; visible brown areas are likely iron-oxide staining or matrix.
Formation & geological history
Forms when silica-rich groundwater fills cavities in volcanic rock, depositing chalcedony and later tiny quartz crystals. Commonly Cenozoic or older, depending on the host volcanic rocks.
Uses & applications
Used as a decorative and lapidary specimen, in jewelry, cabochons, bookends, and mineral collections; generally not used structurally.
Geological facts
“Druzy” describes a coating of many minute crystals rather than a separate mineral. The sparkle comes from thousands of reflective quartz crystal faces.
Field identification & locations
Identify by its cavity-lining texture, glassy sparkle, hardness, and translucent banding; quartz will scratch glass and resist a steel knife. Common sources include Brazil, Uruguay, Mexico, Morocco, and the western United States.
