igneous

Granite Glacial Erratic

Intrusive Phaneritic Felsic Rock (Granite)

Hardness: 6-7 (Mohs scale); Color: light gray to tan with salt-and-pepper mineral grains; Luster: Vitreous to dull (weathered); Crystal structure: Phaneritic (coarse-grained visible crystals); Major minerals: Quartz, Feldspar, Mica.

Hardness: 6-7 (Mohs scale)
Color: light gray to tan with salt-and-pepper mineral grains
Luster: Vitreous to dull (weathered)

Identified March 4, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the slow cooling of silica-rich magma deep underground (plutonic). This specific specimen shows signs of glacial transport—surface rounding and smoothing caused by being carried and deposited by ice during the Pleistocene epoch.

Uses & applications

Larger boulders of this type are used in landscaping, shoreline protection (riprap), and as architectural accents. Crushed granite is a primary material for road base and concrete aggregate.

Geological facts

This specimen is likely a glacial erratic, meaning it was moved by a glacier and deposited in a location where the local bedrock is different. Granite is the most common igneous rock in Earth's continental crust.

Field identification & locations

Field identification is based on the visible interlocking grains of translucent quartz and opaque feldspar. Its rounded shape and position in loose soil suggest it was tumbled by water or ice. Found globally in glaciated regions or areas of exposed cratons.

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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.

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