Granodiorite or Diorite

Physical Properties

Hardness: 6-7 on Mohs scale, Color: speckled black and white or gray (salt and pepper appearance), Luster: dull to slightly shiny, Texture: phaneritic (coarse-grained)

Formation & Geological History

Formed by slow cooling of magma deep underground (intrusive). Composed mainly of plagioclase feldspar, quartz, hornblende, and biotite.

Uses & Applications

Commonly used for crushed stone, construction, landscaping, and sometimes as dimension stone.

Geological Facts

Diorite is often called 'salt and pepper' rock due to its speckled appearance. It was used by ancient civilizations for carving and sculpture.

Field Identification & Locations

Identified by its speckled black and white appearance and lack of foliation. Common in continental crust and mountain-building regions.

Identified on: 4/25/2026

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