Granite

Physical Properties

Hardness: 6-7 (Mohs); Color: Mottled grey, white, and tan with black specks; Luster: Dull to vitreous; Crystal structure: Phaneritic (visible interlocking crystals); Cleavage: Indistinct in hand specimen; Specific gravity: 2.63 - 2.75

Formation & Geological History

Formed from the slow cooling of silica-rich magma deep beneath the Earth's surface (plutonic). Found in continental crust plates; this specimen likely suggests a Paleozoic or Precambrian age depending on locality.

Uses & Applications

Used widely in construction for countertops, floor tiles, and monuments. High durability makes it ideal for abrasive industrial uses and architectural cladding.

Geological Facts

Granite is the most common rock found in the Earth's continental crust and is unique to Earth among the planets in our solar system. The word comes from the Latin 'granum', meaning a grain.

Field Identification & Locations

Identify by looking for a 'salt and pepper' appearance with crystals large enough to see with the naked eye. It will scratch glass and won't fizz with acid. Very common in mountainous regions or riverbeds near mountain runoff.

Identified on: 4/17/2026

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