igneous

Granite

Hardness: 6-7 on Mohs scale. Color: Mottled pink, gray, and white with dark flecks. Luster: Vitreous to dull. Crystal structure: Phaneritic (coarse-grained) containing quartz, feldspar, and biotite mica. Specific Gravity: 2.63 to 2.75.

Hardness: 6-7 on Mohs scale
Color: Mottled pink, gray, and white with dark flecks
Luster: Vitreous to dull

Identified April 11, 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 (plutonic). They are primarily Found in continental crust and date back billions of years or as recently as the Cenozoic era.

Uses & applications

Extensively used in construction as dimension stone, countertops, tiling, monuments, and as crushed stone for road base and concrete aggregate.

Geological facts

Granite is the most common rock in the Earth's continental crust. Mount Rushmore is carved into a massive granite batholith in the Black Hills of South Dakota.

Field identification & locations

Identify by its 'salt and pepper' appearance and interlocking visible crystals. It is found in mountain ranges and ancient shield areas like the Canadian Shield. For collectors, look for high-contrast mineral combinations.

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