Abstract
The occurrence of the zinc-mica hendricksite and of zincian and man-ganoan varieties of phlogopite at Franklin, New Jersey, has been described by Frondel and Ito (1966). The present note records similar micas from the nearby zinc deposit at Sterling Hill. The geology and general mineralogy of the occurrence has been described by Palache (1935) and by Metsger, Tennant and Rodda (1958). Nine partial analyses are cited in Table 1. The occupancy of the octahedral layer has been calculated to a total of three cations on the assumption that the Fe and Mn are wholly present in the divalent state. On this basis, following rules for the nomenclature of the trioctahedral micas earlier suggested, the material of analyses 6 and 7 corresponds to hendricksite, that of analysis 9 to zincian and manganoan phlogopite and that of the remaining analyses to zincian and manganoan biotite. These micas as a group contain more Mg and Fe and less Zn and Mn, with a higher Zn/Mn ratio, than do the related micas from Franklin (Fig. 1).
