an ore of iron consisting of the oxide or carbonate of iron mixed with clay or sand.
See under Clay.
See also: Clay, Ironstone
clay ironstone
clay ironstone
[′klā ′ī·ərn‚stōn] (petrology) A clayey rock containing large quantities of iron oxide, usually limonite.A clayey-looking stone occurring among carboniferous and other rocks; contains 20-30% iron.