Diorite (River Pebble)

Dull luster (unpolished), grey and white salt-and-pepper appearance, phaneritic texture with visible mineral grains, Mohs hardness of 6 to 7, high density.

Formed from the slow cooling of magma beneath the Earth's surface in volcanic arcs and mountain-building regions. This specimen has been rounded into a pebble shape by water erosion in a river or coastal environment.

Used in construction as crushed stone or 'trap rock', historical use for sculpture (like the Code of Hammurabi), and as decorative landscaping stones.

Diorite is often called 'gray granite' by laypeople, but it contains little to no quartz. In ancient Egypt and Mesopotamia, it was prized for its extreme hardness and used for monumental carvings.

Identify in the field by its speckled, coarse-grained texture and lack of visible pink potassium feldspar. Commonly found in areas with past subduction zone activity and in riverbeds as water-worn pebbles.