igneous
Granite Pebble with Quartz/Feldspar Vein
Intrusive Felsic Igneous Rock (Granite)
Hardness: 6-7 on Mohs scale. Color: Speckled black-and-white dioritic/granitic side mixed with pinkish-orange orthoclase feldspar and white/milky quartz. Luster: Vitreous to dull. Texture: Phaneritic (coarse-grained) and water-rounded/smooth.…
- Hardness
- 6-7 on Mohs scale
- Luster
- Vitreous to dull
Identified More igneous →
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Physical properties
Hardness: 6-7 on Mohs scale. Color: Speckled black-and-white dioritic/granitic side mixed with pinkish-orange orthoclase feldspar and white/milky quartz. Luster: Vitreous to dull. Texture: Phaneritic (coarse-grained) and water-rounded/smooth. Cleavage: Indistinct in overall rock, individual feldspar grains show 2 planes at nearly 90 degrees.
Formation & geological history
Formed deep underground from the slow cooling of magma rich in silica, potassium, and sodium. The distinct contact line shows a granite/diorite matrix cross-cut by a pegmatitic vein or contact zone rich in K-feldspar and quartz. It was later eroded and rounded into a river cobble or beach pebble by water action.
Uses & applications
Landscaping, decorative pebble collections, lapidary tumbling, and educational geological specimens demonstrating cross-cutting relationships.
Geological facts
This pebble shows a classic geological contact between two different composition zones, smoothed out naturally by coastal or river erosion over thousands to millions of years.
Field identification & locations
Identified by the distinct sharp contact between speckled granitoid material (biotite/hornblende with plagioclase) and the orange/pink orthoclase feldspar with quartz. Common along glacial drift areas, riverbeds, and ocean beaches worldwide.
