A powdered substance placed on a cue's tip to increase its friction and thereby decrease slippage between the tip and cue ball. Cue "chalk" is not actually chalk (calcium carbonate) at all, but a compound of silica and aluminum oxide. Chalk is sold in compressed, dyed (most commonly blue) cubes wrapped on five sides with a paper label, and is applied (properly) in a manner similar to lipstick on the mouth. Chalk is essential to shots involving spin, and failure to use it frequently during a game is likely to lead to miscuing.45 Modern cuechalk was co-invented by pro player William A. Spinks and engineer William Hoskins. See also talc, often incorrectly referred to as "hand chalk".