Randomly take 6, divide them into two groups, and weigh them on the balance. If it is balanced, the little pearl is between the remaining two pearls, and then it is called a light pearl.

If the balance is unbalanced in the triplet, then the pearl is in the triplet on the lighter side. Take two of these three at random and put them on the balance. If it is balanced, the rest is small pearls; If it is unbalanced, the light one is a small pearl.