sedimentary
Conglomerate
Conglomerate (clastic sedimentary rock)
Hardness: 6.5-7 (variable based on clasts); Color: Variable greys, tans, and whites; Luster: Dull/Earthy; Structure: Clastic, containing rounded pebbles in a fine-grained matrix; Cleavage: None
- Hardness
- 6
- Color
- Variable greys, tans, and whites
- Luster
- Dull/Earthy
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Physical properties
Hardness: 6.5-7 (variable based on clasts); Color: Variable greys, tans, and whites; Luster: Dull/Earthy; Structure: Clastic, containing rounded pebbles in a fine-grained matrix; Cleavage: None
Formation & geological history
Formed by the lithification of rounded gravel and pebbles, typically in high-energy environments like riverbeds, shorelines, or alluvial fans. These specimens can range from recent to hundreds of millions of years old.
Uses & applications
Used primarily in the construction industry as coarse aggregate for concrete and road building. Occasionally used as ornamental stone if it contains attractive pebbles.
Geological facts
Conglomerate is often called "puddingstone" because the rounded clasts resemble raisins or nuts in a pudding. It indicates that a fast-moving water source once existed in the area where it was found.
Field identification & locations
Identify by looking for rounded rocks or 'pebbles' cemented together in a solid mass. It is found globally in areas with ancient river systems. Collectors look for unique inclusions or colorful pebbles within the matrix.
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