Rare technical term for the aluminum ore bauxite. The more common Japanese word is ボーキサイト.
See also: ボーキサイト
水礬土鉱 is sometimes used as another name for bauxite.
The standard modern term for bauxite; 水礬土鉱 is a rare, technical synonym.
The kanji 水 (water), 礬 (alum), 土 (earth), and 鉱 (ore) together suggest a hydrated aluminum ore. The exact derivation is uncertain; the term is a rare technical coinage.