Mineral Species: Sphaerosiderite

Chemical Formula: FeCO3

Chemical Name: Iron Carbonate

Mineral Class: Carbonate

Mineral Notes: Sphaerosiderite is a variety of Siderite that forms botryoidal nodules rather than the more commonly found rhombohedral crystals. This usual form of Siderite has the same crystal structure as Calcite, except that Fe 2+ ions replace Ca 2+ in the metal positions. It is found in bedded sedimentary iron ores and as a vein deposit with other metal ores. It is a major iron ore mineral and is often mined for its metal content. It is also significanlty easier to smelt than other iron ores.

Description: Spherical aggregates of black Sphaerosiderite upon a matrix. This is a very unusual form of the iron carbonate which normally forms rhomboherdral crystals. Some of the aggregates are fused, giving rise to botryoidal-like formations. Where these have grown on one another, the eleongation has an almost stalactitic-like form. A very unusual mineral oddity.

Location: Basaltbrucke, Steinheim, Hessen, Germany.