Crystal Bay, Ascension Island, Saint Helena, Ascension and Tristan da Cunha

   Located close to the Mid-Atlantic Ridge, and nearly halfway between Africa and the horn of South America, Ascension is a volcanic island, a fact clearly reflected in this sand sample: polished black-gray grains of basalt; reddish ash (scoria); yellowish-green crystals of olivine, and shiny black obsidian. The abundance of olivine crystals lends the bay its name. Hints of the marine organisms living in the coast’s wave-pounded shallows are also present in this sand. A worn brownish-purple sea urchin spine lies near center, cross-sections revealing
the concentric interior structure of the spines are seen at 7 and 9 o’clock. The black and white shard in the upper right is a fragment
of snail shell. The island’s coastlines are constantly hammered by the waves that serve to round and polish these grains.

courtesy of the CIA World Factbook