The Where of Mineral Names: Todorokite, Todoroki Mine, Yoichi District, Shiribeshi Subprefecture, Hokkaidō Prefecture, Japan

When it comes to aesthetic specimens, todorokite does not readily spring to mind. Even though a widespread, common mineral, it is not seen in many collections. Mindat.org lists no fewer than 465 localities. Some of these are seafloor nodules found in the Indian Ocean, Pacific Ocean, and the Red Sea, where todorokite is the “principal manganese oxide in deep sea manganese nodules” (Anthony et al. 1997, p. 569). But not all todorokite specimens are dull and unappealing. The yellow and black concretionary todorokite-birnessite specimens found on the western shore of the Chesapeake Bay, Calvert County, Maryland, are not only attractive, but they are also scientifically interesting biominerals (https://www.irocks.com/chesapeakebiominerals-hazen-article; accessed May 2022). Todorokite, together with other manganese derivatives, can be a product of fungal and bacterial activity (de la Torre and Gomez-Alarcon 1994; Burford, Kierans, and Gadd 2003; Frankel and Bazylinski 2003); it is also a component of some dendrites and rock varnish (McKeown and Post 2001). Todorokite (fig. 2), (Na,Ca,K,Ba,Sr)1-x (Mn,Mg,Al)6O12·3–4H2O, is a hydrated Figure 1. Map of Japan showing the location of the Todoroki mine on Hokkaido Island; prepared by William Besse.