sedimentary

Conglomerate

Polymictic conglomerate; rounded clasts cemented in a fine-grained matrix

AI-generated identification · may be incorrect

Likely quartz- and feldspar-rich pebbles in a dark brown, iron-oxide-stained matrix; clastic texture, dull to earthy luster, no consistent cleavage, and estimated Mohs hardness 5–7 for the clasts. The rounded inclusions and visible cement distinguish it from an igneous rock, though the photograph alone cannot confirm c…

Identified August 14, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms when gravel is deposited by energetic rivers, alluvial fans, or shorelines and later compacted and cemented, commonly by silica, calcite, or iron oxides. Age is indeterminate from the image and may range from young Quaternary deposits to ancient sedimentary formations.

Uses & applications

Used locally as building or decorative stone and is mainly collected as a field specimen; this small, ordinary piece has little commercial value.

Geological facts

Conglomerate records transport distance and depositional energy: rounded clasts generally indicate substantial abrasion before burial.

Field identification & locations

Look for rounded pebbles larger than 2 mm embedded in a contrasting matrix; a hand lens, acid test for calcite cement, and examination of a fresh surface help confirm it. Common worldwide in river and fan deposits.