Rock Identifier
River Pebbles (Mixed Suite) (Mixed lithologies: Quartzite and Gneiss) — metamorphic
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

Identified More metamorphic

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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.