sedimentary
Conglomerate
Conglomerate (clastic sedimentary rock)
Hardness: Variable (typically 2-7 depending on clasts and matrix); Color: Tan/brown matrix with multicolored rounded pebbles; Luster: Dull/earthy; Structure: Clastic with rounded clasts >2mm; Specific Gravity: 2.2–2.8.
- Hardness
- Variable (typically 2-7 depending on clasts and matrix)
- Color
- Tan/brown matrix with multicolored rounded pebbles
- Luster
- Dull/earthy
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: Variable (typically 2-7 depending on clasts and matrix); Color: Tan/brown matrix with multicolored rounded pebbles; Luster: Dull/earthy; Structure: Clastic with rounded clasts >2mm; Specific Gravity: 2.2–2.8.
Formation & geological history
Formed in high-energy environments like fast-flowing rivers, alluvial fans, or beaches where water rounds large rock fragments. Over time, these sediments are buried and lithified with a fine-grained matrix of silt, clay, or chemical cement (calcite/quartz).
Uses & applications
Used in the construction industry as coarse aggregate for concrete and roadbeds. Some high-quality specimens with colorful 'puddingstone' appearances are used for decorative architecture or polished as unique lapidary items.
Geological facts
Conglomerate is often called 'puddingstone' because it resembles a fruit pudding. It is geologically significant because it indicates a high-energy environment was present at the time of deposition, showing where ancient rivers or shorelines once existed.
Field identification & locations
Identify by looking for rounded rock fragments (clasts) cemented within a finer-grained matrix. Look for it along riverbeds, coastal cliffs, and mountain fronts. Collectors look for 'matrix-supported' vs 'clast-supported' textures and interesting mix-ins like jasper or quartz pebbles.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone (Quartz-rich)
Arenite (SiO2)
sedimentary
Sandstone (with man-made markings)
Arenite (composed primarily of Quartz, SiO2)
sedimentary