bog iron
bog iron
A general term for a soft, spongy, and porous deposit of impure hydrous iron oxides formed in bogs, marshes, swamps, peat mosses, and shallow lakes by precipitation from iron-bearing waters and by the oxidizing action of algae, iron bacteria, or the atmosphere; a bog ore composed principally of limonite that is commonly impregnated with plant debris, clay, and clastic material. It is a poor-quality iron ore, in tubular, pisolitic, nodular, concretionary, or thinly layered bodies, or in irregular aggregates, in level sandy soils, and esp. abundant in the glaciated northern regions of North America and Europe (Scandinavia).
A term commonly applied to a loose, porous, earthy form of "limonite" occurring in wet ground.