sedimentary
Conglomerate
Conglomerate (clastic sedimentary rock)
Variable hardness (clasts usually harder than matrix), multicolored (greys, whites, tans), dull to earthy luster, contains rounded clasts (>2mm) in a fine-grained matrix of silt or clay.
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Physical properties
Variable hardness (clasts usually harder than matrix), multicolored (greys, whites, tans), dull to earthy luster, contains rounded clasts (>2mm) in a fine-grained matrix of silt or clay.
Formation & geological history
Formed in high-energy environments like river beds, beaches, or alluvial fans where rounded gravel and pebbles are deposited and later lithified by mineral cement such as silica, calcite, or iron oxide.
Uses & applications
Used primarily as aggregate in the construction industry for roads and concrete; occasionally used as ornamental stone if the clasts are colorful or unique.
Geological facts
Often called 'puddingstone' because of its appearance. It is distinct from breccia, which contains angular rather than rounded fragments. Conglomerates can date from any geological period where water flow was sufficient to move large pebbles.
Field identification & locations
Identified by the presence of large, rounded stones clearly embedded within a finer material. Found globally in ancient riverbeds and mountain runoff areas. Collectors look for unique 'puddingstone' varieties that polish well.
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