igneous

Granite (Dioritic or Hornblende-rich)

Phaneritic Plutonic Felsic to Intermediate Igneous Rock

Hardness: 6-7 (Mohs scale), Color: Mottled black and white/cream, Luster: Vitreous to dull, Crystal Structure: Phaneritic (coarse-grained visible crystals), Cleavage: Varies by mineral (perfect for feldspar, poor for quartz), Specific Gravity: 2.6-2.7

Identified March 20, 2026More igneous →

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Physical properties

Formation & geological history

Formed through the slow cooling and crystallization of magma deep beneath the Earth's surface. This allows large mineral crystals to grow. Common in batholiths and continental crust, with varying geological ages from Precambrian to Cenozoic.

Uses & applications

Extensively used in construction for countertops, floor tiles, and dimensional stone. Also used as crushed stone in roadbeds and high-end landscaping. Highly valued as a collector's hand specimen for teaching mineralogy.

Geological facts

Granite makes up a large portion of the Earth's continental crust. El Capitan in Yosemite National Park is one of the world's most famous granite monoliths. The black spots in this specific specimen are likely Hornblende or Biotite mica, while the white/tan is Plagioclase feldspar.

Field identification & locations

Identify in the field by its 'salt and pepper' appearance and visible interlocking crystals. It is found in mountain ranges and ancient shield areas like the Canadian Shield. Unlike sedimentary rocks, it will not scratch easily with a knife and shows no bedding layers.

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