sedimentary

Conglomerate

Conglomeratic Sandstone / Polymictic Conglomerate

Hardness: 6-7 (based on quartz-rich clasts); Color: tan, brown, beige with multi-colored rounded pebbles; Luster: earthy to dull; Structure: clastic texture with rounded rock fragments fixed in a fine-grained matrix; Specific Gravity: varies (approx 2.6-2.8)

Hardness: 6-7 (based on quartz-rich clasts)
Color: tan, brown, beige with multi-colored rounded pebbles
Luster: earthy to dull

Identified May 25, 2026More sedimentary →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Formed in high-energy environments like riverbeds, alluvial fans, or beaches where water transport is strong enough to move and round large pebbles. The clasts are eventually cemented together by minerals like silica, calcite, or iron oxide over millions of years.

Uses & applications

Used primarily in the construction industry as coarse aggregate for concrete and roadbeds. High-quality specimens with colorful 'pebbles' are occasionally polished for use as decorative stones or paperweights in collecting.

Geological facts

Conglomerate is often called 'nature's concrete' because of its appearance. The rounded shape of the individual stones inside indicates they traveled a long distance through water before being deposited.

Field identification & locations

Identify in the field by looking for rounded, water-worn pebbles (clasts) that are larger than 2mm embedded within a finer sandy or silty matrix. Generally found in ancient river channels and sedimentary basins.

Other sedimentary specimens

See all

Sandstone or Siltstone

Arenite (if sandstone)

Sedimentary

Shale or Slaty Mudstone

Argillaceous sedimentary rock

sedimentary

Sandstone

Arenite (primarily SiO2)

sedimentary

Chert Breccia

Brecciated Chert (Microcrystalline Silica)

sedimentary

Sandstone

Arenite

sedimentary

Sandstone (Quartz-rich)

Arenite (SiO2)

sedimentary