The answer to our "Mystery Flower" #liveandlearn question is Lignum Vitae tree. The name means long life or wood of life.
Large stands of Lignum vitae existed on St. John before European colonization. The trees were harvested and land cleared for sugar cane. The Lignum Vitae tree is native to the Virgin Islands and is one of the densest woods known. It resists rot and insects and sinks like a rock when tossed in the ocean.