Metamorphic or Igneous

Granite Gneiss or Granitoid River Rock

Granitoid / Gneiss

Hardness: 6-7 (Mohs scale), Color: speckled grey, white, and tan. Luster: dull to slightly sparkling (due to quartz/feldspar). Rounded shape from water erosion.

Hardness: 6-7 (Mohs scale), Color: speckled grey, white, and tan
Color: speckled grey, white, and tan
Luster: dull to slightly sparkling (due to quartz/feldspar)

Identified May 31, 2026More metamorphic or igneous →

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Physical properties

Hardness: 6-7 (Mohs scale), Color: speckled grey, white, and tan. Luster: dull to slightly sparkling (due to quartz/feldspar). Rounded shape from water erosion.

Formation & geological history

Formed from slow cooling of magma deep underground (if igneous granite) or regional metamorphism (if gneiss), subsequently eroded and tumbled in a river or stream environment.

Uses & applications

Commonly used in landscaping, as aggregate in construction, or decorative river stones.

Geological facts

Rocks like this are typically found in riverbeds and have been smoothed by thousands of years of water action tumbling them against other stones.

Field identification & locations

Identified by its speckled appearance of interlocking quartz, feldspar, and mica grains, and its smoothly tumbled surface. Found in riverbeds and glacial deposits worldwide.

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