Limits of the use of industrial talc—the carbonate effect

If talc ore contains a large proportion of carbonates, air separation is inadequate to obtain products suitable for high-grade applications. An extra chemical treatment, using acids, was evaluated at laboratory level, to further increase the grade of talc concentrates. It was shown that air floated talc, having 10 to 20% of carbonates (magnesite, dolomite and calcite), can be improved, in terms of reflectivity, loss on ignition and iron content.