igneous

Granite

Course-grained intrusive igneous rock

Hardness: 6-7 (Mohs scale); Color: Salt and pepper (gray, white, black); Luster: Vitreous to pearly; Crystal structure: Phaneritic (large visible crystals), mainly potassium feldspar, quartz, and mica; Specific gravity: 2.63 - 2.75

Hardness: 6-7 (Mohs scale)
Color: Salt and pepper (gray, white, black)
Luster: Vitreous to pearly

Identified April 5, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the slow crystallization of magma below Earth's surface. It can be found in continental crust and is often hundreds of millions to billions of years old, forming in tectonic mountain building zones.

Uses & applications

Extensively used in construction for countertops, floor tiles, paving stones, curbing, monuments, and as an aggregate for road base and concrete.

Geological facts

Granite is one of the hardest substances in the world. It makes up the bulk of the continental crust and forms the core of many major mountain ranges like the Himalayas and the Sierras.

Field identification & locations

Identify in the field by its interlocking, 'salt and pepper' crystalline texture where individual minerals like translucent quartz and opaque feldspar are visible. Commonly found in mountainous regions or glacial deposits.

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