Siderite
Mineral FeCO3
Also called Chalybite and Spathic iron
About it
Brown curved rhombs and spheres, heavier than calcite, that fizz only in warm acid. An iron ore; fine crystals come from Cornwall, Portugal's Panasqueira, and Quebec's Mont Saint-Hilaire.
- Type
- Mineral
- Group
- Carbonate, calcite group
- Formula
- FeCO3
- Hardness (Mohs)
- 3.5–4.5
- Specific gravity
- 3.7–3.96
- Streak
- white
- Lustre
- vitreous (glassy), pearly, silky
- Crystal system
- Trigonal
- Colours
- yellowish brown, brown, grey, greenish, reddish brown
- Transparency
- translucent, transparent
- Cleavage and fracture
- perfect rhombohedral
Typical values: real specimens vary. For more, see mindat.org.