igneous

Granite

Phaneritic Plutonic Rock (Granite)

Hardness: 6-7 (Mohs scale); Color: Mottle of gray, white, black, and pink; Luster: Dull to vitreous; Crystal structure: Phaneritic (coarse-grained crystals visible to the naked eye); Cleavage: Indistinct; Specific gravity: 2.63 - 2.75.

Hardness: 6-7 (Mohs scale)
Color: Mottle of gray, white, black, and pink
Luster: Dull to vitreous

Identified April 12, 2026More igneous →

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Physical properties

Formation & geological history

Granite forms from the slow crystallization of magma below Earth's surface. It is a plutonic intrusive rock, often forming large masses called batholiths. It usually dates from millions to billions of years old across various geological eras.

Uses & applications

Extensively used in construction (countertops, floor tiles, paving stones), as dimensional stone in monuments/statues, and as crushed stone for road base and railroad ballast.

Geological facts

Granite is the primary rock making up the Earth's continental crust. It is highly resistant to acid rain and mechanical wear, which is why it has been used for thousands of years, notably by the Ancient Egyptians for temples and sarcophagi.

Field identification & locations

Identify in the field by its 'salt and pepper' appearance and visible crystals of quartz, feldspar, and mica. It is found in mountain ranges and Shields (like the Canadian Shield). Collectors should look for large interlocking crystals of minerals like pink Potassium Feldspar or shiny Muscovite/Biotite.

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