igneous
Granite / Diorite (Granitic Pebble)
Intrusive Felsic/Intermediate Igneous Rock
Hardness 6-7 on Mohs scale; phaneritic (coarse-grained) texture showing salt-and-pepper pattern; colors include gray, white, and black; dull to vitreous luster; massive structure with poor cleavage in bulk form; specific gravity ~2.6-2.8.
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Physical properties
Hardness 6-7 on Mohs scale; phaneritic (coarse-grained) texture showing salt-and-pepper pattern; colors include gray, white, and black; dull to vitreous luster; massive structure with poor cleavage in bulk form; specific gravity ~2.6-2.8.
Formation & geological history
Formed through the slow cooling and crystallization of magma deep beneath the Earth's surface (plutonic formation). The rounded pebble shape indicates secondary erosion and transport by water or glacial activity.
Uses & applications
Commonly used in construction as crushed stone, dimension stone for countertops and monuments, railway ballast, and decorative landscaping rock.
Geological facts
Granite makes up a large portion of Earth's continental crust. Salt-and-pepper granites get their contrasting look from white/gray feldspar and quartz intermixed with dark amphibole or biotite mica.
Field identification & locations
Identified in the field by its interlocking crystalline texture with visible mineral grains of uniform size. Very common worldwide in glacial till, riverbeds, and mountainous regions. Minimal commercial value for individual landscape pebbles.
