sedimentary
Conglomerate
Conglomerate (Clastic Sedimentary Rock)
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).
- Hardness
- Variable (typically 6
- Color
- Grey, tan, or brown
- Luster
- Dull/Earthy matrix with smooth clasts
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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.
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