Magnetite bombs at El Laco volcano, Chile

The origin of apatite iron ores of the Kiruna type remains controversial, e specially the formation of almost pure magnetite that constitutes large par ts of major deposits. The best preserved ores of this type occur on the fla nks of El Lace, a Plio-Pleistocene volcano in the Chilean Andes. Based on r ecent studies a group of workers argues that the El Lace deposits were form ed by hydrothermal fluids. However, existence of ballistic volcanic bombs c omposed of radiating porous aggregates of magnetite crystals in some of the orebodies, demonstrates that apatite iron ores can form directly from a me lt.