At ordinary ambient temperatures, it is a green-brown ionic solid consisting of iron(II) cations Fe2+ and carbonate anions CO2−3.

[8] Care must be taken to exclude oxygen O2 from the solutions, because the Fe2+ ion is easily oxidized to Fe3+, especially at pH above 6.0.

[7] Ferrous carbonate also forms directly on steel or iron surfaces exposed to solutions of carbon dioxide, forming an "iron carbonate" scale:[3] The dependency of the solubility in water with temperature was determined by Wei Sun and others to be where T is the absolute temperature in kelvins, and I is the ionic strength of the liquid.

[9] Ferrous carbonate has been used as an iron dietary supplement to treat anemia.

[11] Ferrous carbonate is slightly toxic; the probable oral lethal dose is between 0.5 and 5 g/kg (between 35 and 350 g for a 70 kg person).