sedimentary

Ferruginous Conglomerate

Conglomerate with Iron-Oxide Matrix (SiO2 + Fe2O3/FeO(OH))

AI-generated identification · may be incorrect

Hardness: 6-7 (clasts), 4-5 (matrix); Color: Dark brown, rusty red, and grey; Luster: Dull/Earthy; Structure: Clastic (coarse-grained); Cleavage: None (breaks across grains); Specific Gravity: 2.6 - 3.2 (varies by iron content)

Hardness: 6-7 (clasts), 4-5 (matrix)
Color: Dark brown, rusty red, and grey
Luster: Dull/Earthy

Identified March 24, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed in high-energy fluvial environments (rivers) or alluvial fans where rounded rock fragments are deposited and later cemented together by iron-rich groundwater precipitating minerals like hematite or goethite. Age ranges from Precambrian to Cenozoic depending on the local basin.

Uses & applications

Used primarily as low-grade construction aggregate, fill material in road building, or as a decorative stone in landscaping. Historically, some high-iron variants were prospected as minor iron ores.

Geological facts

Conglomerates are often called 'puddingstone' because the rounded clasts resemble fruit in a pudding. Because the clasts are rounded, they indicate the material was transported a significant distance by water before lithification.

Field identification & locations

Identify in the field by the 'concrete-like' appearance with large, rounded pebbles embedded in a finer, rusty-colored cement. Often found in ancient riverbeds or mountain foothills. It feels heavier than standard sandstone due to iron content.