@vickyveritas
My geochemist partner looked at the #Blackstone in her long ago dissertation, looking at the clearly #mafic #greenschist facies, which may be ocean basin (maybe a mantle plume interacting), with some odd alkaline basalts, analogous to, maybe, #Iceland. Maybe it was oceanic crust between Avalonia and Gondwana. She thinks this tuff is mafic, based on setting, but she hasn’t put it in front of polarizing filters beneath a microscope. She wants to. Much work to do.