lithophagous

from The Century Dictionary.

• Eating stones; swallowing gravel, as a bird.
• Perforating or penetrating stones, as the Lithophaga; lithodomous.

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

• adjective Eating or swallowing stones or gravel, as the ostrich.
• adjective Eating or destroying stone; -- applied to various animals which make burrows in stone, as many bivalve mollusks, certain sponges, annelids, and sea urchins. See lithodomus.

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

• adjective zoology Eating or swallowing stones or gravel.
• adjective zoology Eating or destroying stone, like some mollusks, sponges, annelids, and sea urchins.