Siderite

Siderite is a mineral that is composed of iron, carbon, and oxygen. It is typically found in sedimentary rocks such as limestone and shale, and is often associated with other minerals such as quartz and calcite.

Siderite can range in color from yellow to brown to grey, and has a dull to glassy luster. It is sometimes used as an iron ore, as it contains a relatively high percentage of iron, and is also used as a pigment in paint and ceramics.