The distribution is not random and follows the following repeating sequence: 6, 0, 4, 5, 1, 3, 2, 0, 0, 5, 1, 0, 3, 4, 0, 0, 5, 0, 1, 0. This means on average, each obstacle cleared yields 2 Gems. This pattern does not include 25 gems yielded from the Gem Box.