This Technical Report describes a gravimetric method for the determination of the loss in mass of nonoxidized iron ores, when ignited at 1000 °C. This method is applicable to a concentration range of a mass fraction of −3,0 % to 7,0 % loss on ignition in natural iron ores, iron ore concentrates and agglomerates, and sinters. The method is not applicable to the following: processed ores containing metallic iron (direct reduced iron); natural or processed ores in which the sulfur content is higher than a mass fraction of 0,2 %; internationally traded ores with combined water greater than 2,5 %. NOTE 1 Loss on ignition can be used as an estimate of combined water. NOTE 2 This method is intended for in-house use and is not intended for referee purposes.