sedimentary

Conglomerate

Polymictic conglomerate; clast-bearing sedimentary rock cemented by silica, calcite, or iron oxides

AI-generated identification · may be incorrect

Pebble- to cobble-sized rounded clasts in a finer sandy matrix, with tan, gray, reddish, and brown coloration and dull, earthy luster. Hardness is variable, commonly about 5–7 for siliceous material; no consistent cleavage or crystal structure, and specific gravity is typically 2.2–2.7.

Identified September 6, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed when transported gravel accumulates in energetic rivers, alluvial fans, or shorelines and becomes compacted and cemented. Its exact age cannot be determined from the image; conglomerates range from Precambrian to modern geological settings.

Uses & applications

Used locally as building stone, decorative aggregate, and landscape rock; attractive polished pieces may be collected, though this specimen appears primarily of educational interest.

Geological facts

The rounded clasts indicate substantial transport before burial, unlike breccia, whose fragments are angular. Mixed clast colors and compositions indicate a polymictic variety.

Field identification & locations

Identify it by visibly rounded pebbles embedded in a finer matrix; a hand lens should reveal contrasting clast boundaries and cement. Common worldwide in river-channel and basin deposits; typical value is $5–$25 for a hand specimen, or $25–$75 for an attractive polished piece.