igneous

Granite

Granite (Phaneritic igneous rock)

Hardness (Mohs): 6-7; Color: Greyish-white with black specks; Luster: Vitreous to dull; Crystal structure: Phaneritic (large, visible crystals of quartz, feldspar, and mica); Specific gravity: 2.63 to 2.75

Color: Greyish-white with black specks
Luster: Vitreous to dull

Identified May 15, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the slow cooling of silica-rich magma deep underground (plutonic). This process allows large crystals to grow. It is found in continental crust and dates from the Precambrian to Cenozoic eras.

Uses & applications

Extensively used in construction, countertops, monuments, paving stones, and as a decorative building stone due to its durability.

Geological facts

Granite makes up the majority of the Earth's continental crust. Mount Rushmore is carved into a granite batholith. Yosemite National Park's famous Half Dome is composed of Granodiorite, a close relative of granite.

Field identification & locations

Identify by its 'salt and pepper' appearance and visible interlocking crystals. Common in mountain ranges and shield regions. Collectors look for unique mineral inclusions like large garnets or 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