·noun An indigo-blue variety of quartz.
II. Siderite ·noun Formerly, magnetic iron ore, or loadstone.
III. Siderite ·noun Any plant of the genus Sideritis; ironwort.
IV. Siderite ·noun A meteorite consisting solely of metallic iron.
V. Siderite ·noun 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.