igneous

Granite

Granite (Phaneritic igneous rock)

Hardness: 6-7 on Mohs scale; Color: Mottled black, pink, and greenish-gray; Luster: Vitreous to dull; Structure: Phaneritic (coarse-grained) crystalline; Cleavage: Depends on individual minerals (perfect for mica, poor for quartz); Specific Gravity: 2.63 to 2.75

Hardness: 6-7 on Mohs scale
Color: Mottled black, pink, and greenish-gray
Luster: Vitreous to dull

Identified April 5, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the slow crystallization of silica-rich magma beneath Earth's surface (intrusive). The large cooling time allows for the visible mineral grains seen in the specimen.

Uses & applications

Widely used in construction, countertops, monuments, paving stones, and as crushed stone for aggregate. Polished specimens are used in jewelry and decorative carvings.

Geological facts

Granite makes up a large portion of the Earth's continental crust. It is one of the hardest and most durable natural stones, which is why it has been used in architecture since Ancient Egypt (e.g., the Red Pyramid).

Field identification & locations

Identify in the field by its 'salt and pepper' appearance and interlocking coarse crystals. It is commonly found in mountain ranges (orogenic belts) and ancient continental shields. Look for the presence of quartz, feldspar, and biotite mica.

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