igneous

Granite (Weathered)

Plutonic Igneous Rock (Granitic)

Hardness: 6-7 on Mohs scale; Color: Gray, pinkish, and white mottling; Luster: Dull to vitreous; Crystal structure: Phaneritic (coarse-grained); Cleavage: None (fractures irregularly); Specific gravity: 2.63 to 2.75.

Hardness: 6-7 on Mohs scale
Color: Gray, pinkish, and white mottling
Luster: Dull to vitreous

Identified March 26, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the slow cooling of silica-rich magma deep underground. This specimen shows surface weathering and lichen growth, suggesting exposure to the elements for decades. Geological age varies by site, often ranging from 100 million to 300 million years old.

Uses & applications

Used widely in construction as dimension stone for countertops, flooring, and monuments. Coarse granite is also crushed for road base and railroad ballast. This specific rough specimen is used as landscape rock.

Geological facts

Granite is the primary component of the Earth's continental crust. It is one of the hardest natural stones and was used by ancient civilizations, like the Egyptians, to build pyramids and obelisks.

Field identification & locations

Identify by its 'salt and pepper' appearance caused by interlocking crystals of quartz, feldspar, and mica. Check for a speckled texture that doesn't rub off. Highly common in mountain ranges like the Rockies or Appalachians. Collectors should look for unweathered surfaces to see crystal clarity.

Other igneous specimens

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Blue Apatite

Fluorapatite (Ca5(PO4)3F)

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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

Magnetite

Iron(II,III) oxide (Fe3O4)

mineral

Blue Apatite

Apatite (Group), Ca5(PO4)3(F,Cl,OH)

mineral

Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

mineral

Magnetite

Magnetite (Fe3O4)

mineral