Siderite is roughly the equivalent of calcite but with iron replacing the calcium. Siderite derives its name from the Greek word sideros which refers to the iron content of the mineral. The color is gray, yellow, yellowish brown, greenish-brown, reddish brown, brown and sometimes gray.

The specific gravity of siderite is 3.96. This means that a piece of siderite would weigh 3.96 times as much as an equal volume of pure water would; in other words, it is heavy. The hardness of siderite is around 4 in the Moh’s scale and this is a bit harder than other common carbonate minerals like calcite and dolomite. A piece of siderite would be harder than a copper penny and softer than a steel knife blade. The hardness can be used to help identify siderite from other minerals.