Pick out the wrong statement.

• Insulating refractories used in place of regular refractory bricks are usually called light weight refractories, and they have similar composition as heavy bricks.
• Graphite refractories are also called plumbago refractories.
• Superduty fireclay bricks correspond to a pyrometric cone equivalent of 26-28.
• Calcined magnesite is also called dead burnt magnesite.