Source : Webster's Revised Unabridged Dictionary (1913)

Siderite \Sid"er*ite\, n. [L. sideritis loadstone, Gr. ????,
   ????, of iron, from ???? 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.

   2. (Bot.) Any plant of the genus {Sideritis}; ironwort.

Source : WordNet®

siderite
     n 1: iron ore in the form of ferrous carbonate [syn: {chalybite}]
     2: a meteorite consisting principally of nickel and iron