This is still a poorly categorised mineral (perhaps due to lack of study samples?), originally described from near Havana, La Habana Province, Cuba. It is a magnesium iron silicate that is not yet formally approved as a species pending more work. This specimen is very rich with the material, dark black masses within the lightweight matrix. For the mineralogist with research facilities access, this could be a fun one to play with. It is also big, and will yield many study samples for exchange and work. Besides, how many minerals do you see from old Cuban mines? Note late 1800s AE Foote label.