Zinc Mica from Franklin Furnace, New Jersey

Abstract

PLATY crystals of a dark mica occur in hancockite-bearing rocks from Franklin Furnace, New Jersey, and electronprobe analysis shows that the mica has high zinc (19.8 per cent) and manganese (12.5 per cent) oxide contents, corresponding to about 40 and 30 per cent respectively of the zinc and manganese end-members. So far as we are aware, no description of such a mineral has previously been published. This communication reports analytical, optical and X-ray data for two samples of the mica, one from the collection of the Department of Mineralogy and Petrology, Cambridge, the other from a hancockite–axinite rock presented by Prof. C. Frondel.