metamorphic
Quartzite Pebble (or River Agate/Chert)
Silicon Dioxide (SiO2)
Hardness: 7 on Mohs scale. Color: Tan, brown, translucent yellowish-grey. Luster: Waxy to vitreous. Structure: Microcrystalline/cryptocrystalline aggregate. Fracture: Conchoidal to uneven. Specific Gravity: ~2.65.
- Hardness
- 7 on Mohs scale
- Color
- Tan, brown, translucent yellowish-grey
- Luster
- Waxy to vitreous
Identified More metamorphic →
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Physical properties
Hardness: 7 on Mohs scale. Color: Tan, brown, translucent yellowish-grey. Luster: Waxy to vitreous. Structure: Microcrystalline/cryptocrystalline aggregate. Fracture: Conchoidal to uneven. Specific Gravity: ~2.65.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone or silica precipitation in sedimentary environments, followed by mechanical erosion and rounding by water action in riverbeds or beaches.
Uses & applications
Commonly collected as river rocks, used in lapidary work (tumbling and polishing), landscape decorative stone, and aggregate in construction.
Geological facts
Water-worn pebbles like this acquire their smooth, rounded shape through thousands of years of natural friction against sand and other stones in river currents or ocean surf.
Field identification & locations
Identify in the field by its high hardness (scratches glass easily), smooth rounded shape, and waxy surface luster. Very common in riverbeds, gravel pits, and coastline beaches worldwide.
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