River Rock with Quartz Vein

Hardness 6-7, dark brown/greenish-black matrix with distinct orange/tan veins, dull to slightly waxy luster when wet, fine-grained groundmass

Formed by volcanic activity where magma cooled quickly at or near the Earth's surface. Later, hydrothermal fluids filled fractures in the rock, depositing quartz or calcite veins. Rounded shape is due to river or glacial tumbling over thousands of years.

Commonly used in landscaping, decorative stone, and sometimes collected for tumbling.

The distinct bands are veins where a different mineral (often quartz or a carbonate) crystallized inside a crack in the host rock long after the original rock formed.

Easily identified by the contrasting veins cutting through a darker, fine-grained host rock. Commonly found in riverbeds, glacial deposits, and beaches.