Siderite with Arsenopyrite
Siderite Crystals on Galena
CHEMISTRY - FeCO3
CRYSTALLOGRAPHY - Hexagonal
CRYSTAL GROWTH AND HABITS - Siderite commonly forms rhombohedral crystals; it can also be tabular, prismatic or scalenohedral. Crystal faces are often curved or stepped; it can be massive to granular. Siderite can also be botryoidal or globular, stalactitic or earthy.
COLOR AND OPTICAL PROPERTIES - The color of Siderite can vary from yellow to brown and reddish brown. It can also be greenish gray or greenish brown. It sometimes weathers to produce and iridescence.
HARDNESS - 3.5 - 4
SPECIFIC GRAVITY - 3.8 - 3.9
LUSTER - Vitreous
STREAK - White to slightly brownish
BREAKABILITY - Very good rhobohedral cleavage {1011}, uneven fracture; brittle.
OCCURRENCE - Siderite is found as a sedimentary deposit associated with shale or coal. It is also found in metal bearing hydrothermal veins.
ASSOCIATED MINERALS - Calcite, Quartz, Dolomite, Fluorite, Barite, Galena, Pyrite.
MINERAL NAME - From the Greek for iron.