igneous

Crushed Granite Gravel

Granite (composed primarily of Quartz, Alkali Feldspar, and Plagioclase Feldspar)

Hardness: 6-7 Mohs; Color: Salt and pepper (pink, gray, white, and black); Luster: Dull to vitreous; Crystal Structure: Phaneritic (coarse-grained); Cleavage: Imperfect; Specific Gravity: 2.63-2.75

Hardness: 6-7 Mohs
Color: Salt and pepper (pink, gray, white, and black)
Luster: Dull to vitreous

Identified March 4, 2026More igneous →

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Physical properties

Hardness: 6-7 Mohs; Color: Salt and pepper (pink, gray, white, and black); Luster: Dull to vitreous; Crystal Structure: Phaneritic (coarse-grained); Cleavage: Imperfect; Specific Gravity: 2.63-2.75

Formation & geological history

Formed by the slow cooling of magma deep beneath the Earth's surface (plutonic formation), typically during Orogeny events millions of years ago. These specific specimens are mechanically crushed and screened from larger quarry deposits.

Uses & applications

Extensively used in construction for road base, railway ballast, concrete aggregate, decorative landscaping, and driveways.

Geological facts

Granite is the most common rock type found in the Earth's continental crust. It is so durable that it was used by Ancient Egyptians to build temples and line the insides of the Great Pyramid of Giza.

Field identification & locations

Identify in the field by its speckled 'salt and pepper' appearance and visible interlocking crystals. Common in mountainous regions or shield areas like the Canadian Shield. For collectors, look for versions with high potassium feldspar content for a deep pink/red color.

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Blue Apatite

Fluorapatite (Ca5(PO4)3F)

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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)

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Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

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Blue Apatite

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

mineral

Magnetite

Magnetite (Fe3O4)

mineral