sedimentary

Conglomerate

Conglomerate (Clastic sedimentary rock)

Hardness: Variable based on clasts (usually 5-7); Color: Brown, tan, and grey clasts in a lighter matrix; Luster: Dull/Earthy; Crystal Structure: Amorphous/Clastic; Cleavage: None (fractures around clasts); Specific Gravity: 2.1-2.6.

Hardness: Variable based on clasts (usually 5-7)
Color: Brown, tan, and grey clasts in a lighter matrix
Luster: Dull/Earthy

Identified March 29, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed by the lithification of rounded gravel and boulders (clasts) larger than 2mm, usually deposited in high-energy environments like riverbeds, alluvial fans, or beaches. Geological age ranges from Precambrian to Holocene.

Uses & applications

Used primarily in the construction industry as coarse aggregate for concrete and road stone. Rarely used for decorative stone if it contains attractive minerals like jasper or quartz.

Geological facts

Conglomerates are often called 'puddingstone' because they resemble a fruit pudding. They are essential for geologists to determine the direction and energy level of ancient water flows.

Field identification & locations

Identify in the field by looking for rounded rock fragments (clasts) cemented within a finer-grained matrix (sand or clay). Common in ancient river basins and coastal areas worldwide.

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