igneous

Granite Cobble

Plutonic Granite

Hardness (Mohs scale): 6 to 7. Color: Mottled white, pink, and gray due to feldspar, quartz, and mica. Luster: Dull (weathered) to vitreous (fresh break). Crystal Structure: Phaneritic (coarse-grained). Cleavage: Imperfect (quartz) to perfect (feldspar). Specific Gravity: 2.63 to 2.75.

Luster: Dull (weathered) to vitreous (fresh break)

Identified March 22, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the slow cooling of silica-rich magma deep underground (plutonic) over millions of years. This specific specimen shows signs of water-rounding, suggesting it was transported by a river or glacier during the Holocene or Pleistocene epochs.

Uses & applications

Used widely in construction (crushed stone, countertops, dimension stone), landscaping, and as an educational tool for teaching mineralogy and rock cycles.

Geological facts

Granite is the primary component of the Earth's continental crust. Its name comes from the Latin 'granum', meaning a grain, in reference to its coarse-grained texture. It's one of the hardest and most durable common rocks found on the surface.

Field identification & locations

Identify in the field by its 'salt and pepper' or mottled appearance and visible crystal interlocking. It is commonly found in mountainous regions or glacial till. For collectors, look for versions with unusually large crystals (pegmatite) or unique color variations.

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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