mineral
Druzy quartz geode
Quartz, silicon dioxide (SiO₂), microcrystalline druzy coating
AI-generated identification · may be incorrectWhite to cream, sugar-like sparkling crystals lining a cavity; vitreous luster, trigonal crystal structure, no cleavage, conchoidal fracture, Mohs hardness 7, and specific gravity about 2.65. The specimen appears natural but may be cut or polished externally.
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Physical properties
White to cream, sugar-like sparkling crystals lining a cavity; vitreous luster, trigonal crystal structure, no cleavage, conchoidal fracture, Mohs hardness 7, and specific gravity about 2.65. The specimen appears natural but may be cut or polished externally.
Formation & geological history
Forms when silica-rich groundwater deposits quartz crystals on the walls of a gas cavity or vug in volcanic rock, commonly during late-stage hydrothermal alteration. The exact geological age cannot be determined from the photograph; such geodes range from Paleozoic to Cenozoic.
Uses & applications
Used as a decorative and lapidary specimen, in jewelry, bookends, and mineral collections; quartz is also important in glass, electronics, and industrial abrasives.
Geological facts
“Druzy” describes a dense coating of tiny crystals rather than a separate mineral. Sparkle increases when the surface is illuminated because many crystal faces reflect light.
Field identification & locations
Identify by its cavity lined with tightly packed, hard, glassy quartz crystals that scratch ordinary glass; calcite is softer and may effervesce in dilute acid. Common sources include Brazil, Uruguay, Mexico, Morocco, and the United States.
