igneous

Granite (with alteration)

Granite (Felsic intrusive igneous rock)

Hardness: 6-7 (Mohs scale); Color: Mottled orange, tan, and grey (likely due to Potassium Feldspar and Plagioclase); Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained) crystalline; Cleavage: Generally poor in the rock mass, though individual minerals have distinct cleavage.

Hardness: 6-7 (Mohs scale)
Luster: Vitreous to dull

Identified February 17, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the slow cooling of silica-rich magma deep underground (plutonic). The orange/tan coloration often indicates weathering or iron-staining of the feldspar minerals over geological time scales, involving millions of years.

Uses & applications

Used extensively in construction for countertops, floor tiles, and paving stones. Is also a heavy-duty material for monuments and riprap in civil engineering.

Geological facts

Granite is the primary rock type that makes up the bulk of the Earth's continental crust. It is incredibly durable and resistant to acid rain, making it a favorite for outdoor sculptures and memorials.

Field identification & locations

Identify in the field by its 'salt and pepper' or multicomponent crystalline look. It is found globally in mountainous regions or ancient shield areas. Collectors should look for large, interlocking crystals of quartz and feldspar.

Other igneous specimens

See all

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