Clay ironstone

A clay-rich ironstone.
i. A compact hard, dark, gray or brown, fine-grained sedimentary rock consisting of a mixture of argillaceous material (up to 30%) and iron carbonate (siderite), occurring in layers of nodules or concretions or as relatively continuous irregular thin beds, and usually associated with carbonaceous strata, esp. overlying a coal seam in the coal measures of the United States or Great Britain; a clayey iron carbonate, or an impure siderite ore occurring admixed with clays. The term has also been applied to an argillaceous rock containing iron oxide (such as hematite or limonite).

See Also: blackband ironstone

ii. A sideritic concretion or nodule occurring in clay ironstone and other argillaceous rocks, often displaying septarian structure.

Ref: AGI


See: ironstone, iron clay