Perché non ci sono nuove statue nella Miniera d'oro?

Philosopher's Stone is a Warlord and operates by the very same rules as the other Warlords:

The statues stop appearing after 12 attacks on the Philosopher's Stone in one turn, which can be seen in Philosopher's Stone abilities. The ability is triggered only when the Philosopher's Stone is attacked, which means that character's abilities will not trigger statue spawn: