sedimentary

Ferruginous Conglomerate (or Iron-Rich Concrete/Slag)

Clastic Sedimentary (Silicon Dioxide/Iron Oxide matrix)

AI-generated identification · may be incorrect

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 February 21, 2026More sedimentary →

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Physical properties

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.