igneous

Granite Cobble

Felsic intrusive igneous rock

Hardness: 6-7 on Mohs scale. Color: predominantly white and grey with black flecks. Luster: Dull (weathered) to vitreous. Crystal structure: Phaneritic (visible crystals). Cleavage: Imperfect. Specific gravity: 2.63-2.75.

Hardness: 6-7 on Mohs scale
Color: predominantly white and grey with black flecks
Luster: Dull (weathered) to vitreous

Identified May 20, 2026More igneous →

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Physical properties

Formation & geological history

Formed through the slow cooling of silica-rich magma beneath the Earth's surface. This particular specimen has been rounded by fluvial (river) or glacial transport, likely during the Quaternary period.

Uses & applications

Crushed stone for road construction, architectural stone, and decorative landscaping. High-quality granite is used for countertops and monuments.

Geological facts

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

Field identification & locations

Identify by its 'salt and pepper' appearance and hardness (it will scratch glass). Commonly found in riverbeds, glacial moraines, and mountainous regions.

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Blue Apatite

Fluorapatite (Ca5(PO4)3F)

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