igneous
Granite Pebble
Granite (plutonic rock composed of Quartz, Potassium Feldspar, Plagioclase, and Biotite/Amphibole)
Hardness: 6-7 on Mohs scale. Color: Mottled pinkish-tan, grey, white, and black. Luster: Vitreous to dull (weathered). Texture: Phaneritic (coarse-grained) and rounded due to river or glacial erosion. Cleavage: Indistinct in bulk specimen, though feldspar grains exhibit cleavage planes.
- Hardness
- 6-7 on Mohs scale
- Color
- Mottled pinkish-tan, grey, white, and black
- Luster
- Vitreous to dull (weathered)
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Physical properties
Hardness: 6-7 on Mohs scale. Color: Mottled pinkish-tan, grey, white, and black. Luster: Vitreous to dull (weathered). Texture: Phaneritic (coarse-grained) and rounded due to river or glacial erosion. Cleavage: Indistinct in bulk specimen, though feldspar grains exhibit cleavage planes.
Formation & geological history
Formed deep within the Earth's crust through the slow cooling and crystallization of felsic magma. This specific piece is a stream- or beach-rounded pebble shaped by mechanical weathering and water transport over geological timescales.
Uses & applications
Widely used as construction aggregate, crushed stone, decorative landscaping rock, and in polished form for countertops and monuments. Common educational sample.
Geological facts
Granite makes up a large portion of Earth's continental crust. Over millions of years, erosion exposes granite plutons, which then break down into cobbles and pebbles found in riverbeds and beaches worldwide.
Field identification & locations
Identified in the field by its distinct interlocking 'salt-and-pepper' or pinkish crystalline texture containing visible quartz and feldspar grains, smoothed into a rounded cobble shape by water or ice. Found extensively in mountainous regions, river valleys, and glacial till deposits.
