igneous

Granite

Hardness: 6-7 on Mohs scale. Color: Typically light-colored (white, pink, gray) with dark mineral grains. Luster: Vitreous to dull. Crystal structure: Phaneritic (coarse-grained), interlocking crystals. Cleavage: Poor due to interlocking grains. Specific gravity: 2.6-2.7 g/cm³.

Hardness: 6-7 on Mohs scale
Luster: Vitreous to dull

Identified October 4, 2025More igneous →

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Physical properties

Formation & geological history

Formed from the slow crystallization of magma below Earth's surface (intrusive igneous). It is typically associated with continental crust and often forms the core of mountain ranges. Geological age varies greatly, from Precambrian to Cenozoic, depending on the specific intrusion event.

Uses & applications

Widely used in construction for countertops, flooring, paving, and building facades due to its durability and aesthetic appeal. Also used for monuments, sculptures, and occasionally as an aggregate.

Geological facts

Granite is one of the most abundant intrusive igneous rocks in the Earth's continental crust. Its name comes from the Latin 'granum', meaning 'grain', in reference to its coarse-grained structure. The 'speckled' appearance is due to the visible, distinct mineral grains.

Field identification & locations

Identify in the field by its coarse-grained texture, light color with visible dark specks, and its hardness (it cannot be scratched by a steel knife). It is commonly found in mountainous regions, shield areas, and as the basement rock of continents worldwide. Look for large exposures in quarries or eroded landscapes. Collectors appreciate its variety in color and texture.

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