sedimentary

Conglomerate

Conglomerate (clastic sedimentary rock)

AI-generated identification · may be incorrect

Hardness: 6.5-7 (variable based on clast types); Color: Tan, brown, gray, and reddish-pink; Luster: Dull/Earthy; Structure: Clastic with rounded grains/pebbles larger than 2mm; Cleavage: None (breaks across pebbles).

Hardness: 6
Color: Tan, brown, gray, and reddish-pink
Luster: Dull/Earthy

Identified March 7, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed in high-energy environments such as fast-flowing rivers, alluvial fans, or beaches where water movement rounds rock fragments. Over millions of years, these sediments are buried and lithified with a matrix of sand, silt, or chemical cement (like calcite or silica).

Uses & applications

Commonly used as a decorative stone in construction, a low-grade aggregate for roads, and occasionally as an ornamental stone in landscaping or interior design when polished ('Puddingstone').

Geological facts

Conglomerates are often referred to as 'pudding stones' because they resemble fruit cake or pudding. They are significant because the rounded shape of the pebbles indicates they traveled a long distance from their source.

Field identification & locations

Identify in the field by looking for rounded, water-worn pebbles larger than peas embedded in a finer-grained matrix. Found globally in ancient riverbeds and mountain fronts. Collectors look for unique 'matrix' colors or rare clast compositions.