noun
limonite; brown hematite
A mineral term for a brown iron ore; used in geology and mining contexts.
褐鉄鉱は鉄の重要な原料の一つです。
Limonite is one of the important raw materials for iron.
The kanji 褐 (brown), 鉄 (iron), and 鉱 (ore) directly describe the mineral. The reading is on'yomi.