igneous

Granite Cobble

Granite (Phaneritic Igneous Rock)

Hardness: 6-7 Mohs; Color: Pink, grey, and white mottled; Luster: Dull to vitreous; Crystal Structure: Phaneritic (coarse-grained); Composition: Quartz, Potassium Feldspar, and Plagioclase.

Hardness: 6-7 Mohs
Color: Pink, grey, and white mottled
Luster: Dull to vitreous

Identified April 11, 2026More igneous →

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Physical properties

Hardness: 6-7 Mohs; Color: Pink, grey, and white mottled; Luster: Dull to vitreous; Crystal Structure: Phaneritic (coarse-grained); Composition: Quartz, Potassium Feldspar, and Plagioclase.

Formation & geological history

Formed through the slow crystallization of magma below the Earth's surface (intrusive). This specific specimen shows signs of fluvial or glacial transport, resulting in its rounded 'cobble' shape.

Uses & applications

Used in construction as crushed stone, dimension stone for countertops and monuments, and occasionally as decorative landscaping rock.

Geological facts

Granite is the most common rock found in the Earth's continental crust. The pink hue in this specimen is caused by the presence of Orthoclase (potassium feldspar).

Field identification & locations

Identify in the field by its speckled 'salt and pepper' appearance and visible crystal grains. It is extremely common in glacial till and riverbeds across North America.

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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