1. (Science: chemical) 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 colour. Called also sparry iron, spathic iron. A meteorite consisting solely of metallic iron.
An indigo–blue variety of quartz.
Formerly, magnetic iron ore, or loadstone.
2. (Science: botany) Any plant of the genus Sideritis; ironwort.
Origin: L. Sideritis loadstone, Gr, of iron, from iron.