During the colonial days of the West Indies, building supplies were much in demand. Ingenious builders looked to the sea for some of their construction materials, and came away with a particularly good item, one that started out pliable but soon turned to rock. Or at least rock-like.
Brain corals, so named for their brain-tissue-like patterns, could be cut from the ocean when soft and pliable, and when dried they became rock-like, a perfect building material for the sugar plantations that the Danes built across the Caribbean. This particular block can be found in the ruins of the Annaberg Sugar Plantation at Virgin Islands National Park.