sedimentary
Ferruginous Conglomerate (or Iron-Rich Concrete/Slag)
Clastic Sedimentary (Silicon Dioxide/Iron Oxide matrix)
Hardness: 5-7 (variable); Color: Dark brown, black, rust-red, with multi-colored clasts; Luster: Dull to sub-metallic; Structure: Heterogeneous/Clastic; Specific Gravity: 2.6 - 3.5 (high if iron-rich).
- Hardness
- 5-7 (variable)
- Color
- Dark brown, black, rust-red, with multi-colored clasts
- Luster
- Dull to sub-metallic
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 5-7 (variable); Color: Dark brown, black, rust-red, with multi-colored clasts; Luster: Dull to sub-metallic; Structure: Heterogeneous/Clastic; Specific Gravity: 2.6 - 3.5 (high if iron-rich).
Formation & geological history
Formed by the lithification of rounded pebbles and sand grains cemented together by mineral-rich fluids, often iron oxides or silica. It can also represent anthropogenic (man-made) ferro-concrete or industrial iron slag based on the dark, bubbly texture seen in some areas.
Uses & applications
Commonly used as fill material in construction, as a source for crushed stone, or for architectural stone. In some cases, it can be an indicator of iron-ore deposits.
Geological facts
Conglomerates are like 'nature's concrete'; their rounded pebbles indicate transport through high-energy environments like riverbeds or coastal wave zones. The reddish tint in this sample suggests hematite or limonite oxidation.
Field identification & locations
Identify by looking for rounded rocks 'glued' together in a darker matrix. This specimen has a scorched or vitrified appearance which often occurs in urban areas near old blast furnaces or roadworks (clinker). Found in alluvial deposits or old industrial sites.
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