Arts, 'Carom' balls were made from Ivory for over 100 years.One thing to be aware of, some sets came from the factory with ivory cue ball and clay balls. Full ivory sets with sixteen ivory balls were pretty rare. Billiard balls, three ball sets, of all ivory were more common.
A maker of pool balls, I think Brunswick, posted a $10,000 reward for an ivory substitute which was absolutely huge at the time. Most of the tusk wasn't suitable to make pool balls, only two or three balls could be made from a single tusk! I assume that the same small area was all that was used for ivory ferrules and joints too.
I think Bakelite was the first plastic used for balls and some of the early plastic developed fine cracks similar to ivory. Very tough for anyone less than an expert to determine ivory. Customs tests with a hot needle I believe.
Hu
From the 'Purest' which is called 'Clear Zanzibar ivory' tightest grain, hardly visible, you can get 3-4 'Carom' size balls!
Then some balls are made from 'Further up the tusk' which are called 'Barkies' heavier grained.
In 1963 at Bensinger in Chicago they still had 'Clay Pool Balls' with 'ivory cue balls up till about 66.
I've Never seen a 'Complete set of Pool balls' that were All ivory!