n. [ L. sideritis loadstone, Gr. &unr_;&unr_;&unr_;&unr_;, &unr_;&unr_;&unr_;&unr_;, of iron, from &unr_;&unr_;&unr_;&unr_; iron. ] 1. (Min.) (a) Carbonate of iron, an important ore of iron occuring generally in cleavable masses, but also in rhombohedral crystals. It is of a light yellowish brown color. Called also sparry iron, spathic iron. (b) A meteorite consisting solely of metallic iron. (c) An indigo-blue variety of quartz. (d) Formerly, magnetic iron ore, or loadstone. [ 1913 Webster ]

2. (Bot.) Any plant of the genus Sideritis; ironwort. [ 1913 Webster ]