sedimentary
Conglomerate
Conglomerate (clastic sedimentary rock)
Hardness: variable (depends on clast composition); Color: mottled, multi-colored; Luster: earthy/dull; Structure: rounded clasts (>2mm) in a fine-grained matrix; Cleavage: none.
- Hardness
- variable (depends on clast composition)
- Color
- mottled, multi-colored
- Luster
- earthy/dull
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Physical properties
Hardness: variable (depends on clast composition); Color: mottled, multi-colored; Luster: earthy/dull; Structure: rounded clasts (>2mm) in a fine-grained matrix; Cleavage: none.
Formation & geological history
Formed through the lithification of rounded gravel and boulders. These are typically deposited in high-energy environments like fast-flowing rivers, alluvial fans, or glacial wash where water rounds the stones over time.
Uses & applications
Used primarily in the construction industry as coarse aggregate for concrete and road fill. Occasionally used as ornamental stone if the clasts are colorful or unique.
Geological facts
Conglomerates are often called 'puddingstone' because they resemble a fruit pudding. Curiosity Rover discovered conglomerate rocks on Mars, providing evidence of ancient flowing water on the planet.
Field identification & locations
Identify in the field by looking for large, rounded pebbles or cobbles cemented together. Commonly found in ancient riverbeds or mountain bases. Collectors look for 'healed' fractures where the stone has broken through the pebbles.
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