igneous

Granite

Granite (composed primarily of Quartz SiO2, Alkali Feldspar KAlSi3O8, and Plagioclase Feldspar)

Hardness: 6-7 on the Mohs scale. Color: Mottled grey, white, and pink with dark flecks. Luster: Vitreous to dull. Crystal structure: Phaneritic (coarse-grained visible crystals). Cleavage: None (though individual feldspar crystals within may show cleavage). Specific Gravity: 2.63 to 2.75.

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

Identified January 11, 2026More igneous →

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Physical properties

Formation & geological history

Formed by the slow crystallization of magma below the Earth's surface (intrusive). Geological age spans from the Archean Eon to the Cenozoic. It forms the bulk of the Earth's continental crust.

Uses & applications

Extensively used in construction for countertops, floor tiles, paving stones, and monuments due to its durability and aesthetic appeal. Also used as crushed stone for road base and concrete aggregate.

Geological facts

Granite is one of the hardest substances in the world, second only to diamonds and some other gemstones. Mount Everest's summit is unique because it is capped with sedimentary limestone, but the core of the Himalaya range consists largely of granite.

Field identification & locations

Identify in the field by its 'salt and pepper' appearance and visible interlocking crystals. It is found in mountain ranges and continental shields worldwide, such as the Sierra Nevada (USA) or the Scottish Highlands. Collectors look for large, well-defined potassium feldspar crystals (megacrysts) or rare mineral inclusions like tourmaline.

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

Magnetite

Iron(II,III) oxide (Fe3O4)

mineral

Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

mineral

Blue Apatite

Apatite (Group), Ca5(PO4)3(F,Cl,OH)

mineral

Magnetite

Magnetite (Fe3O4)

mineral