Psilomelane is an intriguing natural stone that is a composite of 2 minerals, romanechite and pyrolusite. They are extruded from volcanically active sites in deep ocean waters.  Millions of years later, the action of plate tectonics bring them to the surface for us to discover.  I found this stone at a gem show this Spring and had to buy it!  I designed this bracelet in a rectangular style that contrasts nicely with the whorls in the stone.