Conglomerate

Physical Properties

Hardness: Variable (typically 6.5-7 for quartz clasts); Color: Grey, tan, or brown; Luster: Dull/Earthy matrix with smooth clasts; Structure: Coarse-grained clastic; Cleavage: None (breaks across clasts or through matrix).

Formation & Geological History

Formed through the lithification of rounded gravel and boulders typically deposited in high-energy environments like riverbeds, beaches, or alluvial fans. Geological age varies from Precambrian to Cenozoic.

Uses & Applications

Used primarily as coarse aggregate in the construction industry for concrete and road fill. Occasionally used as a decorative stone in landscaping or interior design (e.g., Puddingstone).

Geological Facts

Conglomerates are known as 'puddingstones' because the rounded clasts resemble raisins in a pudding. They are distinctive because the rounded shape of the rocks inside indicates they were transported long distances by water.

Field Identification & Locations

Identify in the field by looking for rounded pebbles or 'cobbles' larger than 2mm embedded in a finer sandy or silty matrix. Found globally in ancient river systems and shorelines.

Identified on: 4/20/2026

Mode: Standard