sedimentary
Vuggy Quartz / Chert
Silicon Dioxide (SiO2)
Hardness: 7 (Mohs scale), Color: Tan to light brown with white frosting, Luster: Waxy to vitreous in cavities, Structure: Microcrystalline with vugs, Specific Gravity: 2.65
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Physical properties
Hardness: 7 (Mohs scale), Color: Tan to light brown with white frosting, Luster: Waxy to vitreous in cavities, Structure: Microcrystalline with vugs, Specific Gravity: 2.65
Formation & geological history
Formed via chemical precipitation of silica-rich fluids within voids of sedimentary rocks, often replacing carbonates. The 'holes' (vugs) are where minerals or fossils dissolved out.
Uses & applications
Used in landscaping, as a source of silica for industrial glass, and by lapidary hobbyists for tumbling or cabbing.
Geological facts
This specimen shows 'vuggy' texture, where small cavities are lined with macro-crystalline quartz. Chert has been used since prehistoric times to create sharp tools and fire-starters.
Field identification & locations
Identify by its hardness (scratches glass), waxy exterior, and characteristic pitted or porous 'vuggy' surface. Commonly found in riverbeds and limestone outcrops.
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