The Moaning Diamond [Major Artifact]

Said to have been ripped from the ground in a ritual that tortured the earth itself, the Moaning Diamond appears to be an uncut diamond the size of a human fist. At all times, it gives forth a baleful moaning sound, as if in pain. Despite the noise, the Moaning Diamond is not evil (although it was birthed in torture). The wielder of the stone can, three times per day, call upon it to reshape earth and stone as if by the spell stone shape, affecting 5,000 cubic feet of material. The Moaning Diamond can summon an elder earth elemental with maximum hit points (312) that serves the caster until it is slain. Only one such elemental can be summoned at a time; if it is slain, a new creature cannot be summoned for 24 hours. Tales from the past tell of the Moaning Diamond creating stone structures, opening underground chambers where there had been none before, and collapsing entire castles.

Source: Dungeon Master’s Guide (version 3.5), page 281.