Abstract: In a process to produce a synthetic rhombehedral magnetite comprising the steps of:A. Contacting ferrous chloride solution having an Fe.sup.++ concentration of from about 0.9 to 2.4 moles per liter with a stoichiometric amount of carbonate ion;B. heating the mixture to a temperature of from about 70.degree.-90.degree. C.;C. aerating the mixture to oxidize the iron to magnetite having a Fe.sup.++ / total Fe.sup.++ and Fe.sup.+++ ratio of from about 0.25-0.38; andD. recovering the magnetite so produced,the improvement which comprises providing the carbonate in the form of finely divided particles of an average size of less than 3.5 microns.The process wherein said magnetite is calcined at a temperature of from 650.degree.-925.degree. C. in the presence of oxygen to produce alpha ferric oxide is claimed and a synthetic rhombohedral magnetite having a BET surface area of greater than about 13 m.sup.2 /g and an average particle size of less than about 0.08 microns as measures along the long axis is also claimed.

Abstract: A data bearing card having a magnetizable, transparent, colorless coating thereon is disclosed. The coating can comprise a transparent, colorless plastic matrix containing a dispersed particulate crystalline phase. The dispersed phase is prepared by mixing 20-60% of a rare earth compound containing a colorless ferromagnetic ion such as gadolinium with 0.1-5% of titanium dioxide or zirconium oxide, 0.05-2.5% of an inorganic fluoride salt and the balance up to 100% of a glass forming matrix such as inorganic borates. The mixture is heated above its melting point to form a homogeneous melt and subsequently crystallized. The resulting crystalline product can be ground to any desired particle size for dispersion in the transparent plastic matrix.In general, the coating composition is useful in all applications where magnetic coatings are presently used.