sedimentary
Conglomerate
Conglomerate (clastic sedimentary rock)
Hardness varies by cement (usually 6-7 if siliceous); Color: grey, tan, or brown matrix with multicolored inclusions; Luster: dull to earthy matrix with vitreous clasts; Structure: coarse-grained clastic texture containing rounded clasts (pebbles) larger than 2mm.
- Color
- grey, tan, or brown matrix with multicolored inclusions
- Luster
- dull to earthy matrix with vitreous clasts
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Physical properties
Hardness varies by cement (usually 6-7 if siliceous); Color: grey, tan, or brown matrix with multicolored inclusions; Luster: dull to earthy matrix with vitreous clasts; Structure: coarse-grained clastic texture containing rounded clasts (pebbles) larger than 2mm.
Formation & geological history
Formed through the lithification of rounded gravel and pebbles, typically in high-energy environments like riverbeds, alluvial fans, or glacial meltwater streams where water velocity was high enough to transport large particles.
Uses & applications
Used primarily in the construction industry as coarse aggregate for concrete and road base; occasionally used as decorative stone in landscaping or interior flooring.
Geological facts
Conglomerate is often called "puddingstone" because the rounded pebbles in the matrix look like raisins or nuts in a pudding. It serves as a geological indicator of ancient river systems or shorelines.
Field identification & locations
Identify in the field by looking for large, rounded rock fragments (clasts) cemented together in a finer-grained matrix. It is found globally in sedimentary basins. For collectors, look for unique colors or jasper/agate inclusions.
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