metamorphic
River Pebbles (Mixed Suite)
Mixed lithologies: Quartzite and Gneiss
Hardness 6-7 (Mohs), varied colors (pink, grey, white, tan), dull to vitreous luster, crystalline and foliated textures, high durability
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Physical properties
Hardness 6-7 (Mohs), varied colors (pink, grey, white, tan), dull to vitreous luster, crystalline and foliated textures, high durability
Formation & geological history
Formed through regional metamorphism of sandstone (quartzite) and granite or shale (gneiss). These specific pieces were smoothed by fluvial (river) erosion over thousands of years.
Uses & applications
Landscaping, aquarium gravel, decorative stones, and aggregate for construction.
Geological facts
Quartzite is so durable that it can withstand millions of years of chemical and physical weathering. Gneiss is one of the oldest rock types found in Earth's crust, with some specimens dating back over 4 billion years.
Field identification & locations
Look for rounded shapes indicating water transport. Gneiss shows characteristic bonding/striping, while Quartzite has a uniform sugary texture and can scratch glass.
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