Abstract: A particulate carrier material for use with particulate passivated magnesium for injection into molten iron to desulfurize the iron, improve characteristics of the slag and increase iron yield. Material flow of a transport gas and the carrier material is established in a lance prior to inserting the lance into a ladle-contained molten iron, then following insertion the passivated magnesium is added to the material flow. A second embodiment of the invention for iron desulfurization, blends the carrier material and passivated magnesium into a single desulfurization agent. In both embodiments the particulate magnesium is 14-20 mesh with the remaining particulate material being about 200 mesh. The composition of the carrier material is 54-74% calcium oxide, 19-32% aluminum oxide, no more than 4% magnesium oxide, no more than 10% calcium fluoride, no more than 2.5% silicon dioxide, no more than 1.0% iron oxide, no more than 0.025% phosphorus pentoxide, no more than 0.025% titanium dioxide, no more than 0.