Acta Musei Moraviae

Chemical variability of hancockite-epidote-epidote-(Sr) minerals from Franklin, Sussex, New Jersey, USA

Epidote-group minerals from Franklin Sussex, New Jersey, USA, rich in Pb, Sr and Mn were studied in detail using electron microprobe. In a metamorphosed rock composed of epidote group minerals, andradite – grossular, Zn – rich phlogopite and rare baryte distinctly zoned crystals of epidote – epidote-(Sr)-hancockite were identified based on different Pb, Sr and Ca contents. Simple isomorphous and coupled substitution vectors were determined based on our results, one of them indicating presence of piemontite-(Pb) component tending to hypothetical ferripiemontite-(Pb) end-member. Generaly, epidote-group minerals from Franklin are Mn- and Sr-richer and Pb-depleted compared to other hancockite occurrences in the world.