Abstract: A milling assembly for a ball mill has a housing for refining and separating a substrate and a collection vessel for retaining the refined substrate. The housing includes, in vertical order, a lid, at least one milling vessel for receiving milling balls, and a screen with a refining section and apertures. The collection vessel is releasably mounted to a bottom end of the housing. The housing has an orifice arranged therein. The orifice has a valve for selectively allowing gas to pass between an outside and an inside of the housing in an open position of the valve and to seal the housing against the outside in a closed position of the valve. The milling vessel includes a taper for receiving a sealing screw.