igneous

Granite Cobble

Phaneritic Felsic Igneous Rock (Granite)

Hardness: 6-7 on Mohs scale; Color: Mottled gray, white, and black; Luster: Dull to vitreous; Structure: Phaneritic (coarse-grained visible crystals); Composition: Principally Quartz, Feldspar, and Mica; Specific gravity: 2.63 - 2.75

Hardness: 6-7 on Mohs scale
Color: Mottled gray, white, and black
Luster: Dull to vitreous

Identified March 23, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the slow cooling and crystallization of molten magma deep beneath the Earth\'s surface. This specific specimen has been smoothed and rounded by water erosion (fluvial or glacial processes) over thousands of years.

Uses & applications

In this rounded form, they are used as decorative landscaping stones and river rock. In its raw form, granite is essential for construction (countertops, monuments, and aggregate).

Geological facts

Granite makes up a large portion of the Earth\'s continental crust. Because it contains radioactive elements like thorium and uranium, high-density granite can actually emit small, harmless amounts of radon gas.

Field identification & locations

Identify by its 'salt and pepper' appearance and the presence of glass-like translucent quartz grains mixed with opaque white feldspar. Commonly found in riverbeds, glacial moraines, and coastal beaches where water has weathered the edges of the rock.

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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)

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Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

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Blue Apatite

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

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Magnetite

Magnetite (Fe3O4)

mineral