mineral
Quartz geode with drusy quartz crystals
Quartz, silicon dioxide (SiO₂), commonly colorless to milky crystalline quartz
AI-generated identification · may be incorrectTypically hardness 7 Mohs, vitreous luster, white or translucent color, hexagonal crystal structure, and no cleavage (conchoidal fracture). The specimen shows a hollow cavity lined with fine sparkling crystals, possibly with iron-oxide staining or minor associated minerals.
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Physical properties
Typically hardness 7 Mohs, vitreous luster, white or translucent color, hexagonal crystal structure, and no cleavage (conchoidal fracture). The specimen shows a hollow cavity lined with fine sparkling crystals, possibly with iron-oxide staining or minor associated minerals.
Formation & geological history
Forms when silica-rich groundwater deposits quartz inside cavities or vesicles in volcanic rock, sedimentary concretions, or hydrothermal veins. Individual crystals may form over long periods from late Paleozoic to recent geological ages, depending on locality.
Uses & applications
Used as a mineral specimen, lapidary material, and source of silica; attractive geodes are sold for display and collecting. It is generally not jewelry-grade unless crystals are clear and well formed.
Geological facts
The glittering coating is called drusy or druzy quartz. Quartz is one of Earth’s most abundant minerals and is piezoelectric, producing an electrical charge under pressure.
Field identification & locations
Identify by glassy sparkle, hardness sufficient to scratch ordinary glass, six-sided crystal faces, and lack of cleavage; acid does not react. Common sources include Brazil, Uruguay, Mexico, Morocco, and the western United States.
