igneous
Pink Granite (River Pebble)
Felsic intrusive igneous rock (consisting of Quartz, Orthoclase Feldspar, and Plagioclase)
Hardness: 6-7 (Mohs); Color: Pink, reddish-brown, white, and gray; Luster: Dull to vitreous; Crystal Structure: Phaneritic (visible interlocking crystals); Cleavage: Feldspar shows two directions at 90 degrees; Specific Gravity: 2.63-2.75
- Hardness
- 6-7 (Mohs)
- Color
- Pink, reddish-brown, white, and gray
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6-7 (Mohs); Color: Pink, reddish-brown, white, and gray; Luster: Dull to vitreous; Crystal Structure: Phaneritic (visible interlocking crystals); Cleavage: Feldspar shows two directions at 90 degrees; Specific Gravity: 2.63-2.75
Formation & geological history
Formed from the slow cooling of silica-rich magma deep underground (plutonic). The pink hue is caused by potassium feldspar. This specific specimen has been rounded by fluvial (water) erosion in a river or glacial environment.
Uses & applications
Used primarily as construction aggregate, decorative landscaping stone, and architectural facing when found in large slabs. River pebbles are often used in xeriscaping.
Geological facts
Granite makes up a large portion of the Earth's continental crust. The pink color specifically indicates a high concentration of orthoclase feldspar, common in many ancient cratons.
Field identification & locations
Identify by the 'salt and pepper' or multi-colored speckled appearance with visible crystalline grains. Found globally in mountainous regions or areas with glacial till and riverbeds. It will easily scratch glass.
