igneous
Granite (Gneissic / Weathered Pebble)
Felsic intrusive igneous rock (Granite)
Hardness: 6-7 on the Mohs scale. Color: Mottled gray, tan, pinkish-brown, and black. Luster: Dull to vitreous (flecks of mica and quartz). Texture: Medium to coarse-grained phaneritic structure, weathered and rounded edges from erosion.…
- Hardness
- 6-7 on the Mohs scale
- Color
- Mottled gray, tan, pinkish-brown, and black
- Luster
- Dull to vitreous (flecks of mica and quartz)
Identified More igneous →
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Physical properties
Hardness: 6-7 on the Mohs scale. Color: Mottled gray, tan, pinkish-brown, and black. Luster: Dull to vitreous (flecks of mica and quartz). Texture: Medium to coarse-grained phaneritic structure, weathered and rounded edges from erosion. Cleavage: Indistinct in rock mass, though individual feldspar grains show step-like cleavage planes.
Formation & geological history
Formed by the slow crystallization of silica-rich magma deep beneath the Earth's surface (plutonic environment). Over millions of years, tectonic uplift exposed the rock, and mechanical weathering/water action eroded and rounded it into a river pebble or cobble.
Uses & applications
Granite is widely used as a construction material, dimension stone, countertop surface, and crushed aggregate for roads. Small rounded pebbles like this are popular in landscaping, river rock decor, and basic educational rock collections.
Geological facts
Granite makes up a large portion of Earth's continental crust. The sparkly flakes often seen in specimens like this are mica (biotite or muscovite), while the glassy grains are quartz and the opaque blocky grains are feldspar.
Field identification & locations
Identified in the field by its speckled, 'salt-and-pepper' appearance containing interlocking mineral grains of quartz, feldspar, and dark ferromagnesian minerals. Commonly found along riverbeds, beaches, glacial till deposits, and mountainous regions worldwide.
