igneous

Red Granite

Phaneritic Felsic Intrusive Igneous Rock (primarily K-feldspar, Quartz, and Biotite)

Hardness: 6-7 Mohs; Color: Pinkish-red (from Potassium Feldspar) with black specks (Biotite/Hornblende); Luster: Vitreous to dull when weathered; Structure: Phaneritic (coarse-grained, visible crystals); Specific gravity: 2.63 to 2.75.

Hardness: 6-7 Mohs
Luster: Vitreous to dull when weathered

Identified March 22, 2026More igneous →

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Physical properties

Formation & geological history

Formed through the slow cooling of silica-rich magma deep within the Earth's crust (plutonism). Red granites frequently date back to the Precambrian or Paleozoic eras and are often associated with continental crust stable interiors.

Uses & applications

Extensively used as dimension stone for architecture, countertops, and grave markers due to durability. In smaller forms, it is used as decorative landscaping gravel, railroad ballast, or polished as pocket stones.

Geological facts

The red hue is specifically caused by a high concentration of orthoclase (potassium feldspar). If the feldspar is stained by trace amounts of hematite (iron oxide), the red color becomes even more vibrant.

Field identification & locations

Identify in the field by its 'salt and pepper' look but with a red/pink base; it will scratch glass and lacks bedding planes. Commonly found in the Canadian Shield, Scotland, and the Llano Uplift in Texas.

Other igneous specimens

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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

Magnetite

Iron(II,III) oxide (Fe3O4)

mineral

Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

mineral

Blue Apatite

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

mineral

Magnetite

Magnetite (Fe3O4)

mineral