A brown, gray-green, or white mineral, iron (II) carbonate
(FeCO3), found in sedimentary iron
ores and as vein deposits with other ores. Its crystals are rhombohedral
in the hexagonal system and it occurs as massive deposits or in granular
form. Hardness 4, relative density 3.8. Iron
meteorites are sometimes known as siderites.
AND PLANETARY SCIENCE