A mixture of lime with shells, gravel, or stones, in equal proportions, with an equal proportion of water. When dry, this becomes as hard as rock.
Tabby is a building material consisting of lime, sand, water, and crushed oyster shells. It was made and used on the Sea Islands of coastal South Carolina, Georgia, and northern Florida in the Southern United States during the Colonial Period up until the early 1800s as a substitute for bricks, which were rare and expensive because of the absence of local clay. The name comes from the Spanish word, tapia, which means "mud wall".