Rock Identifier
Quartz Vein in Basalt or Sedimentary Host Rock (Silica-veined lithic fragment (SiO2 in host matrix)) — sedimentary
sedimentary

Quartz Vein in Basalt or Sedimentary Host Rock

Silica-veined lithic fragment (SiO2 in host matrix)

Hardness: 7 for the quartz veins (Mohs scale), 3-6 for the host rock; Color: Grayish-brown host with stark white quartz veins; Luster: Vitreous on quartz, dull on host; Crystal structure: Trigonal (quartz); Cleavage: None for quartz (conchoidal fracture); Specific Gravity: ~2.65 for quartz.

Hardness
7 for the quartz veins (Mohs scale), 3-6 for the host rock
Color
Grayish-brown host with stark white quartz veins
Luster
Vitreous on quartz, dull on host
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Physical properties

Hardness: 7 for the quartz veins (Mohs scale), 3-6 for the host rock; Color: Grayish-brown host with stark white quartz veins; Luster: Vitreous on quartz, dull on host; Crystal structure: Trigonal (quartz); Cleavage: None for quartz (conchoidal fracture); Specific Gravity: ~2.65 for quartz.

Formation & geological history

Formed when hydrothermal fluids rich in dissolved silica penetrated fractures or faults within a pre-existing rock body, subsequently cooling and precipitating out crystalline quartz. Weathering and water tumbling later shaped it into a smooth pebble.

Uses & applications

Commonly collected as a curiosity, used in landscaping, rock tumbling, or as a decorative garden stone.

Geological facts

Quartz veins are often referred to by prospectors as 'reefs' and are famous for potentially hosting gold and other precious metal ores in mineralized regions.

Field identification & locations

Easily identified in the field by the striking contrast of hard white quartz ribbons cutting directly through a darker, softer matrix rock. Common in riverbeds, glacial drift, and marine beaches worldwide.

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