igneous

Granite Pebble

Granite (Felsic Plutonic Rock)

Hardness: 6-7 (Mohs); Color: Salt-and-pepper (white, grey, and black); Luster: Dull to vitreous; Crystal structure: Phaneritic (coarse-grained); Specific Gravity: 2.63-2.75

Hardness: 6-7 (Mohs)
Color: Salt-and-pepper (white, grey, and black)
Luster: Dull to vitreous

Identified May 31, 2026More igneous →

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Physical properties

Hardness: 6-7 (Mohs); Color: Salt-and-pepper (white, grey, and black); Luster: Dull to vitreous; Crystal structure: Phaneritic (coarse-grained); Specific Gravity: 2.63-2.75

Formation & geological history

Formed from the slow cooling of silica-rich magma deep underground (plutonic). This specific specimen is an water-worn pebble, likely rounded by river or beach erosion.

Uses & applications

Used widely in construction (countertops, flooring), monuments, and as decorative landscaping stones.

Geological facts

Granite makes up a large portion of the Earth's continental crust. The black spots in this specimen are likely biotite or hornblende, while the white is quartz and feldspar.

Field identification & locations

Identify by its 'salt and pepper' appearance and visible interlocking crystals. Common in mountain ranges and glacial deposits. For collectors, look for hard, speckled rocks that cannot be scratched by a steel knife.

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mineral

Dark Igneous Rock (Likely Basalt or Diabase)

Basalt (extrusive igneous rock) or Diabase (intrusive igneous rock - also known as Dolerite), largely composed of plagioclase feldspar, pyroxene (augite), and sometimes olivine and amphibole. Exact mineralogy would require thin section analysis.

Igneous