Wikipedia says steatite is "relatively soft (because of the high talc content, talc being 1 on Mohs hardness scale), and may feel soapy when touched."

While "The term steatite is sometimes used for soapstone", "It may also denote also a type of ceramic material made from soapstone with minor additives and heated to vitrify (to change or make into glass or a glassy substance, especially through heat fusion)."

Perhaps that's how this piece got its green glaze. It then would be similar to faience, excepting instead of a mostly silica base, it is mostly talc based.