It is generally served with warm milk, which creates a thick froth on the top. Supergene ores rich in sulfides may be concentrated using froth flotation. A flat white has milk (or microfoam) but no froth. During initial processing, ores typically undergo crushing, dense-medium separation, grinding, froth flotation, and drying. Fine coal is cleaned using froth flotation methods. Froth flotation is an important concentration process. Algae can be harvested using microscreens, by centrifugation, by flocculation and by froth flotation. Egg white can also be added to shaken cocktails to create a delicate froth. This renders the ore difficult to treat via the froth flotation technique. Processing is via froth flotation and cyanidation. The beginnings of the revolutionary froth flotation process are associated with graphite mining. Froth flotation was added in the 1920s. These compounds give a permanent froth when shaken with water. Therefore, it is important in the industry for the froth flotation process. The resulting cacao beverage with the froth is named Pozonque.