Granite (Leucogranite)

Physical Properties

Hardness: 6-7 Mohs; Color: Light gray to white with black and tan specks; Luster: Vitreous to dull; Crystal structure: Phaneritic (visible crystals); Cleavage: Perfect in feldspars, none in quartz; Specific gravity: 2.63 - 2.75

Formation & Geological History

Formed from the slow cooling of silica-rich magma deep underground (plutonic). This specimen appears to be a leucogranite due to the dominance of light-colored minerals. It can date from the Archean to the Cenozoic era depending on the specific batholith it originated from.

Uses & Applications

Used extensively in construction (countertops, flooring, monuments), as crushed stone for road base, and as decorative landscape rock or mineral specimens for teaching.

Geological Facts

Granite makes up the majority of the Earth's continental crust. Mount Rushmore is carved into a massive granite batholith. It is one of the hardest and most durable natural stones used by humans.

Field Identification & Locations

Identify in the field by its interlocking 'salt and pepper' crystalline texture and extreme hardness (it will scratch glass). Commonly found in mountainous regions or areas where ancient crust is exposed, such as the Appalachian or Rocky Mountains.

Identified on: 4/15/2026

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