sedimentary
Conglomerate
Conglomerate (Detrital sedimentary rock)
Hardness: 6.5-7 (highly variable based on clast composition); Color: Gray/beige matrix with brown and black rounded clasts; Luster: Dull/Earthy; Crystal Structure: None (clastic texture); Cleavage: None; Specific Gravity: 2.6-2.8
- Hardness
- 6
- Color
- Gray/beige matrix with brown and black rounded clasts
- Luster
- Dull/Earthy
Identified More sedimentary →
Explore Conglomerate in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6.5-7 (highly variable based on clast composition); Color: Gray/beige matrix with brown and black rounded clasts; Luster: Dull/Earthy; Crystal Structure: None (clastic texture); Cleavage: None; Specific Gravity: 2.6-2.8
Formation & geological history
Formed in high-energy environments like riverbeds or alluvial fans where water current is strong enough to transport large, rounded pebbles. Over time, these pebbles are buried and cemented together by minerals like silica or calcite. Age varies by formation location.
Uses & applications
Used primarily as aggregate in the construction industry for concrete and roadbeds. Some attractive specimens are used for ornamental stone or lapidary work.
Geological facts
Conglomerate is often called "puddingstone" because the rounded clasts resemble raisins or fruit in a pudding. It is the sedimentary opposite of breccia, which contains sharp, angular fragments.
Field identification & locations
Identify in the field by looking for rounded pebbles (larger than 2mm) embedded in a finer-grained matrix. Commonly found in ancient river channels or mountain base deposits. Collectors look for unique color contrasts between the pebbles and matrix.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Cone-in-cone structure (Limestone)
Cone-in-cone structure (Secondary Sedimentary Structure)
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary