Also known as orbicular jasper, this rare gemstone is a type of highly silicate rhyolite found only on the coast near Marovao, Madagascar. Rhyolite is an igneous rock, rich in silica. As it cools, sometimes the silica starts to precipitate out of the magma, forming little spheres. Ocean Jasper has typical rhyolite formation except that the entire mass has been converted to pure silica. This deposit of Ocean Jasper can only be seen and collected at low tides. The area has no roads, so the material must be transported by boat.