sedimentary

Rounded conglomeratic river pebble

Polymict conglomerate (lithified gravel), composition uncertain from image

AI-generated identification · may be incorrect

Brown-gray, rounded and weathered, with visible pebble-sized clasts in a finer cement; mostly dull to subvitreous luster. Likely hardness about 5–7 overall, with variable cleavage and density depending on quartz-, feldspar-, and rock-fragment content.

Identified September 2, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed when gravel was deposited by a river or shoreline, then compacted and cemented into conglomerate; subsequent erosion rounded the specimen. Its exact geologic age and source cannot be determined visually.

Uses & applications

Primarily a teaching, landscaping, or collecting specimen; conglomerate may be used locally as aggregate or decorative stone, but this small pebble has negligible industrial value.

Geological facts

The rounded clasts and mixed texture distinguish conglomerate from breccia, whose fragments are angular. The dark grains may include mafic rock or magnetite, while pale grains are likely quartz or feldspar.

Field identification & locations

Look for rounded, contrasting clasts embedded in a cemented matrix; a hand lens and streak, acid, or hardness tests can refine identification. Common in river gravels and sedimentary basins worldwide.