mineral
Milky Quartz Nodule / Geode precursor
Silicon Dioxide (SiO2)
Mohs hardness 7. Color: opaque white to milky white with brown/ochre iron oxide weathering crust. Luster: vitreous to greasy. Crystal system: trigonal/hexagonal. Conchoidal fracture, no cleavage. Specific gravity approx 2.65.
- Luster
- vitreous to greasy
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Physical properties
Mohs hardness 7. Color: opaque white to milky white with brown/ochre iron oxide weathering crust. Luster: vitreous to greasy. Crystal system: trigonal/hexagonal. Conchoidal fracture, no cleavage. Specific gravity approx 2.65.
Formation & geological history
Formed via hydrothermal precipitation or secondary mineral growth inside cavities of volcanic or sedimentary rocks. Silica-rich fluids precipitate quartz layers over time.
Uses & applications
Used in lapidary work, decorative rock collections, gemstone polishing, and as an industrial source of quartz/silica.
Geological facts
Unopened rock nodules with bumpy, knobby quartz exterior surfaces like this one often contain hollow chambers lined with quartz crystals (geodes) or solid chalcedony interiors (thunder eggs).
Field identification & locations
Identified by its hard white quartz mass (scratches glass/steel easily) combined with a rounded, weathered matrix or husk. Commonly found in stream beds, gravel deposits, and volcanic terrains worldwide.
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