Cenozoic Coral at Annaberg Plantation, St. John, U.S. Virgin Islands
Building Image
Building Image
      The images above show one of the buildings at Annaberg Plantation on the north side of the island of St. John in the U.S. Virgin Islands. Annaberg was a sugar plantation built in the 1780s, when St. John was one of the Danish Virgin Islands; hence the Germanic name for this tropical establishment.

     Much of the building consists of randomly sized and shaped pieces of the metamorphic rocks that make up much of the island. Those random sizes and shapes don't make straight edges and corners, so a more workable stone was needed. Builders found that stone locally in the corals that abound in the reefs and on the seafloor surrounding the island. Corals generate masses of calcium carbonate, which isn't as hard as most silicate minerals. That lesser hardness, and the porosity of the coral skeleton, make it relatively easy to cut. The window below, for example, is framed with cut coral in which the living chambers of the individual coral animals can be seen clearly, especially in the enlargement at right.

Stone Image
     The calcium carbonate in the blocks thus has a long history in the construction business. It was first taken from seawater and chemically precipitated by coral as a convenient housing material on the seafloor, where it was in use for centuries. Then it was dragged ashore, cut up, and used by a larger, but less chemically skilled and shorter-lived, builder on land.


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