graniteware

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Iron utensils with a mottled enamel resembling granite.
• noun Earthenware with a speckled glaze resembling granite.

from The Century Dictionary.

• noun Any fine pottery decorated by a more or less exact imitation of the speckled surface of granite; specifically, one of Josiah Wedgwood's pebble-wares, described by him in 1770 as “barely sprinkled with blue” and ornaments gilt.” See pebbleware.
• noun A fine pottery similar to ironstone china, referring to its supposed hardness.
• noun A variety of enameled ironware much used for utensils of cookery, in which the enamel is gray and stone-like, and very durable.

from the GNU version of the Collaborative International Dictionary of English.

• noun a kind of ironware with stone gray enamel.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun Ironware that has been coated with a layer of vitreous enamel with a swirled or speckled pattern resembling granite.
• noun Pottery with the same type of enamel coating.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a kind of stone-grey enamelware