noun an indigo-blue variety of quartz.
2. siderite ·noun formerly, magnetic iron ore, or loadstone.
3. siderite ·noun any plant of the genus sideritis; ironwort.
4. siderite ·noun a meteorite consisting solely of metallic iron.
5. 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.