sedimentary

Conglomerate (pebble conglomerate)

Clastic conglomerate; quartz- and feldspar-rich clasts in a dark, iron-stained matrix

AI-generated identification · may be incorrect

Rounded tan, orange, and pale pebbles are cemented in a dark fine-grained matrix, indicating abrasion before burial. Typically Mohs 6–7 overall, with earthy to dull luster and no consistent cleavage; hardness varies by clast and cement.

Identified August 15, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed when water-rounded gravel accumulated in a river, alluvial fan, or shoreline, then lithified by compaction and silica, carbonate, or iron-oxide cement. Age cannot be determined from the photograph and may range from recent geological periods to Precambrian.

Uses & applications

Used locally as dimension stone, decorative aggregate, landscaping stone, and construction fill; attractive polished pieces may be collected, though it is not usually a gemstone.

Geological facts

The defining feature is rounded pebble-sized clasts; angular fragments would indicate breccia instead. The orange coloration commonly reflects iron oxides such as hematite or limonite.

Field identification & locations

Identify it by contrasting rounded clasts that resist separation from the matrix; inspect a fresh surface and use a dilute acid test only if carbonate cement is suspected. Conglomerates occur worldwide, especially in ancient river channels and basin margins.