Diamonds are hydrophobic (repel water) and readily adhere to grease or oil. A "grease table" uses these physical properties to separate diamonds from alluvial gravels or kimberlite concentrate. The grease table at Stornoway's laboratory is used as a final recovery circuit for diamonds not removed by the X-ray flow sorter. After two passes through the X-ray unit, kimberlite tailings are flushed over a vibrating table covered with a layer of specially formulated grease. While waste rock fragments and minerals are washed away by flowing water and sprayers, diamonds resist being wetted and adhere to the greased surface instead. The diamond laden grease is scraped off the table, boiled in water to remove the grease and cleaned using a solvent degreasing machine. Resultant diamond concentrates are sent to the observation laboratory for hand sorting.