One of the best of this style with excellent luster and form, complete all around! It is a superb specimen for this size range. Chesapeake biominerals, including Hollandite, Todorokite, Romanechite, Birnessite, and other unusual manganese and iron species, form when metal-rich subsurface waters emerge from the face of the cliffs along the western shore of Chesapeake Bay. Microbes exploit the chemical richness of the waters by oxidizing the metals and precipitating minerals in beautifully sculpted masses. The resulting specimens containing mixed amounts of these related species, such as those you see here, are among the finest examples of their style anywhere in the world and are unique in their aesthetic appeal and scientific interest. A portion of all sales goes to support the study of Chesapeake Bay geology through the laboratory of Dr. Robert Hazen.