sedimentary
Conglomerate
Conglomerate (SiO2 primary clasts with lithic matrix)
Hardness: Variable (clasts often 7, matrix 3-6); Color: Brown, tan, orange, with white/clear quartz pebbles; Luster: Dull to earthy matrix with vitreous clasts; Crystal structure: Clastic (rounded grains); Specific gravity: 2.6-2.8
- Hardness
- Variable (clasts often 7, matrix 3-6)
- Color
- Brown, tan, orange, with white/clear quartz pebbles
- Luster
- Dull to earthy matrix with vitreous clasts
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Physical properties
Hardness: Variable (clasts often 7, matrix 3-6); Color: Brown, tan, orange, with white/clear quartz pebbles; Luster: Dull to earthy matrix with vitreous clasts; Crystal structure: Clastic (rounded grains); Specific gravity: 2.6-2.8
Formation & geological history
Formed in high-energy environments such as riverbeds, alluvial fans, or beaches where rounded pebbles are deposited and later cemented together by minerals like silica, calcite, or iron oxide.
Uses & applications
Used primarily in the construction industry as coarse aggregate for concrete and road fill. Occasionally used as a decorative building stone.
Geological facts
Conglomerates are often referred to as 'puddingstone' because the rounded clasts resemble raisins or nuts in a pudding. They are essential indicators of ancient high-energy water environments.
Field identification & locations
Identify in the field by looking for rounded, water-worn pebbles larger than 2mm embedded in a finer-grained matrix. It is commonly found in sedimentary basins and ancient river channels.
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