sedimentary
Conglomerate
Conglomerate (clastic sedimentary rock)
Hardness: 3-7 (variable based on clasts/cement); Color: Tan, brown, rust-red, or gray; Luster: Dull/Earthy; Structure: Clastic, featuring rounded rock fragments (clasts) larger than 2mm embedded in a finer matrix; Cleavage: None.
- Hardness
- 3-7 (variable based on clasts/cement)
- Color
- Tan, brown, rust-red, or gray
- Luster
- Dull/Earthy
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Physical properties
Hardness: 3-7 (variable based on clasts/cement); Color: Tan, brown, rust-red, or gray; Luster: Dull/Earthy; Structure: Clastic, featuring rounded rock fragments (clasts) larger than 2mm embedded in a finer matrix; Cleavage: None.
Formation & geological history
Formed through the lithification of rounded gravel and pebbles, typically in high-energy environments like riverbeds, alluvial fans, or beaches where water action rounds the fragments over time. Most date from various eras depending on local basin history.
Uses & applications
Used primarily as low-grade construction aggregate, fill material, and occasionally as decorative dimension stone if the colors are striking. Not typically used in jewelry due to its coarse, variable nature.
Geological facts
Conglomerate is often called 'puddingstone' because the rounded pebbles look like raisins or plums in a pudding. It differs from breccia, which contains angular fragments, indicating the fragments in conglomerate traveled further from their source.
Field identification & locations
Identify by looking for distinct, rounded 'pebbles' cemented together in a solid mass. It is commonly found in ancient coastal areas or river basins. Collectors look for unique color combinations or rare rock types within the clasts.
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