How is diamond like a freshly waxed car? It repels water, an unusual property for a mineral. Diamond's strong bonding and carbon composition cause its surface to repel water but to readily accept wax and grease. These two properties provide an effective means of separating diamonds from other minerals that come out of mining operations. Washed gravel containing diamonds is flushed with water over a sloping surface covered with a mixture of wax and grease, a "grease table." The diamonds stick to the table, while the wetted waste minerals wash over it. Gem diamonds readily pick up a greasy film, but cleaning with ammonia or a good detergent restores their brilliance.