Carbonates: Siderite

Composition: FeCO₃; magnesium may substitute extensively for iron

Crystal system: Trigonal; crystals commonly rhombohedral, also, massive, granular, botryoidal,
oolitic and earthy forms

1.8.1 siderite Roxbury CT USA

Properties:

• Vitreous to earthy lustre
• Yellowish to reddish brown color
• White streak
• Knife scratches easily (Mohs Hardness 4)
• Above average density
• Three perfect cleavages not at 90^o to each other
• Cleaves rather than fractures unless finegrained
• Not ferromagnetic
• Does not react with dilute hydrochloric acid (HCl); is soluble in warm concentrated hydrochloric
  acid

Occurrence:

Siderite occurs with clays in extensive ironstone layers interbedded with other sedimentary rocks
and with quartz, other carbonates, oxides and sulfides in hydrothermal vein and replacement ore
deposits.

1.8.2 siderite Roxbury CT USA	1.8.3 siderite  Malbon QLD Australia

1.8.4 siderite Malbon QLD Australia	1.8.5 siderite Roxbury CT USA

Ironstone deposits are locally important sources of iron.