Polo is a team sport played on horseback in which the objective is to score goals against an opposing team. Players score by driving a small white plastic or wooden ball into the opposing team’s goal using a long-handled mallet.
Since 1890, the US Polo Association has governed the equestrian team sport of polo played in the United States. Over time, the composition of the ball has changed. The outdoor polo ball is typically made of a high compact plastic, but was formerly made of either bamboo or willow root.
There are few rules governing the ball.
13. OTHER NECESSARYEQUIPMENT
a. Balls shall be within the limits of 3 to 3 ½ inches in diameter and 3 ½ to 4 ½ ounces
21. HOW PLAY IS INTERRUPTED
c. Damaged, Buried Ball.
If the ball becomes damaged to the extent it is unplayable by being chipped, broken, or trodden into the ground the Umpire shall stop the game. What is a chipped, broken, buried, or unplayable ball shall be the sole discretion of the Umpire. If the ball is minorly chipped or broken, the Umpire should not stop the game until it is in such a position that neither team is favored. In the case of a broken ball, the largest piece shall be played.
US Polo Association – uspolo.org
Photo – en.wikipedia.org/wiki/Polo