The attribute which was not common of Indus Valley stamp seals is that the stamps were carved out pure limestone. Option A is correct.
The stamps were made generally of another type of rock: stearite (a magnesium-rich rock composed of mineral talc.
The Indus Valley Civilisation (IVC) was a Bronze Age civilisation in the northwestern regions of the Indian subcontinent, which protracted from 3300 BCE to 1300 BCE.