It is possible to float heavy mineral sands like rutile, anatase, zircon, tourmaline, iron oxides, etc., away from quartz in slightly alkaline systems. Usually in these applications feed is deslimed and conditioned at high-solids with about 150 to 250 g/t of AERO 704 promoter with sufficient soda ash to keep the pH of the rougher float at around 8.5. A small amount of fuel oil may be also added to the ball mill if grinding is carried out. The heavy minerals are floated off in a concentrate running approximately 80% heavy minerals and 20% quartz. Flotation tailings are usually a high-grade quartz sand product. At operations where feldspar occurs with quartz, it may be desirable after a neutral heavy-mineral float to adjust the Al2O3 content of the final quartz product by floating off a quartz-feldspar product with AEROMINE 3030C or AEROMINE 3035C promoters. Rejected in this float are unwanted feldspar, clay, black chert, high-iron spar and rock fragments such as andesite, rhyolite, quartzite, quartz-tourmaline and quartz-hornblend pegmatites. If required, a small amount of AERO 633 depressant may be added to control inadvertent flotation of feldspar. The flotation product has the desired amount of Al2O3, usually 2 to 3.5%.