Heymatt:

What are pool balls made out of? I thought the might be made out of ceramics of some kind.

-- Lea Dean, South Africa

Before 1910 or so, ivory (from Zimbabwean elephants, in particular) was the favored material, six per carcass on average. Polymer science came to the pachyderms' rescue, and for most of the 20th Century, pool balls have been made of synthetics. The best today are made of phenolic resin polymer plastics, if that's not too redundantly repetitive. Unchippable. Unstainable. Unwarpable. Unmeltable. Water and chemical repellant. In it's other lives, phenol resin is used to fuse the layers in heavy-duty plywood, coat or stiffen materials exposed to extreme environments, as an eternally permanent sealer and bonding agent, and as raw material for parts in radios, TVs, electrical appliances, cars, tanks, and high-speed flying things in the aerospace industry. It's almost scary. The stuff won't die.