Unglazed pottery is called bisque or biscuit porcelain. Unglazed pottery is still popular and more expensive than the same piece which had been glazed because the unglazed pottery has to be perfect in every way without cracks.
1 Additional Answer
Hard unglazed pottery is called Parian. It is a marble like unglazed hard porcelain material developed since the 1840s and used most successfully for sculptural antiques. The name is obtained from its close similarity to the white marble mined on the island of Paros though its products cost much less than marble.