
sedimentary
Conglomeratic sandstone or breccia specimen
Quartz-rich clastic sedimentary rock; likely sandstone with pebble-sized quartz, feldspar, and lithic clasts
AI-generated identification · may be incorrectTan-brown, coarse-grained, poorly sorted, and weakly cemented, with prominent white angular to rounded clasts and dark lithic grains. Quartz is Mohs 7 with vitreous luster; the matrix is likely siliceous or calcareous, so hardness and acid reaction may vary.
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Physical properties
Tan-brown, coarse-grained, poorly sorted, and weakly cemented, with prominent white angular to rounded clasts and dark lithic grains. Quartz is Mohs 7 with vitreous luster; the matrix is likely siliceous or calcareous, so hardness and acid reaction may vary.
Formation & geological history
Formed when sand and gravel accumulated in a high-energy river, alluvial-fan, or shoreline environment and lithified by compaction and cementation. Its exact geological age cannot be determined from the photograph.
Uses & applications
Primarily a collecting specimen; related sandstone and conglomerate are used as building stone, aggregate, and occasionally ornamental stone. It has little jewelry value unless unusually colorful, durable, or fossiliferous.
Geological facts
The mixed grain sizes and visible clasts indicate sedimentary transport and deposition rather than a single crystalline mineral. The white material may be quartz, calcite, or weathered feldspar.
Field identification & locations
Identify it by visible rounded or angular grains embedded in a finer matrix; a dilute acid test can distinguish calcite cement by fizzing, while a glass-scratch test helps assess quartz. Common in river, fan, and conglomerate-bearing sedimentary formations worldwide.
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