sedimentary

Conglomerate

Conglomerate (clastic sedimentary rock)

AI-generated identification · may be incorrect

Hardness: Variable (typically 2-7 depending on clasts and matrix); Color: Tan/brown matrix with multicolored rounded pebbles; Luster: Dull/earthy; Structure: Clastic with rounded clasts >2mm; Specific Gravity: 2.2–2.8.

Hardness: Variable (typically 2-7 depending on clasts and matrix)
Color: Tan/brown matrix with multicolored rounded pebbles
Luster: Dull/earthy

Identified March 20, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed in high-energy environments like fast-flowing rivers, alluvial fans, or beaches where water rounds large rock fragments. Over time, these sediments are buried and lithified with a fine-grained matrix of silt, clay, or chemical cement (calcite/quartz).

Uses & applications

Used in the construction industry as coarse aggregate for concrete and roadbeds. Some high-quality specimens with colorful 'puddingstone' appearances are used for decorative architecture or polished as unique lapidary items.

Geological facts

Conglomerate is often called 'puddingstone' because it resembles a fruit pudding. It is geologically significant because it indicates a high-energy environment was present at the time of deposition, showing where ancient rivers or shorelines once existed.

Field identification & locations

Identify by looking for rounded rock fragments (clasts) cemented within a finer-grained matrix. Look for it along riverbeds, coastal cliffs, and mountain fronts. Collectors look for 'matrix-supported' vs 'clast-supported' textures and interesting mix-ins like jasper or quartz pebbles.