igneous
Rock Fragment with Calcite/Quartz Vein
Polymictic Rock Fragment (SiO2 / CaCO3)
Hardness varies (3 to 7 Mohs), dull to vitreous luster, irregular fracture, dark brownish-grey matrix with a white mineral patch (calcite or quartz).
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Physical properties
Hardness varies (3 to 7 Mohs), dull to vitreous luster, irregular fracture, dark brownish-grey matrix with a white mineral patch (calcite or quartz).
Formation & geological history
Formed via weathering, breakdown, or hydro-thermal alteration of larger rock bodies in riverbeds, gravel pits, or mountain soils.
Uses & applications
Common gravel material, road base, soil aggregate, or sample specimen for educational study.
Geological facts
Small pebbles like this often carry tiny veins of quartz or calcite that filled microscopic cracks in the host rock millions of years ago.
Field identification & locations
Identified by the contrast between the dark host matrix and the lighter mineral inlay. Found worldwide in stream beds, gravel deposits, and soils.
