sedimentary
Conglomerate
Conglomerate (clastic sedimentary rock)
Hardness: 3-7 (variable based on clasts); Color: gray, brown, or buff matrix with multicolored rounded pebbles; Luster: dull to earthy; Crystal structure: non-crystalline (clastic texture); Cleavage: none; Specific gravity: 2.6-2.8
- Hardness
- 3-7 (variable based on clasts)
- Luster
- dull to earthy
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Physical properties
Hardness: 3-7 (variable based on clasts); Color: gray, brown, or buff matrix with multicolored rounded pebbles; Luster: dull to earthy; Crystal structure: non-crystalline (clastic texture); Cleavage: none; Specific gravity: 2.6-2.8
Formation & geological history
Formed by the lithification of rounded gravel and pebbles, typically in high-energy environments like riverbeds, beaches, or alluvial fans. Geological age can range from Precambrian to Holocene.
Uses & applications
Primarily used in the construction industry as coarse aggregate for concrete and road base. Occasionally polished for ornamental use or landscaping.
Geological facts
Conglomerates are often referred to as 'puddingstone' due to their appearance. They are important to geologists because the rounded shape of the pebbles indicates they were transported long distances by water.
Field identification & locations
Identify in the field by looking for rounded, water-worn pebbles larger than 2mm embedded in a finer-grained matrix. Found globally in ancient river basins and coastal areas. Commonly collected by beginners due to their unique 'mosaic' look.
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