Permian manganese nodules near Dillon, Montana

They are enriched in many rare elements and contain us much as 2.5 percent zinc, l.3 percent nickel, and 0.22 percent cobalt. The manganese minerals are chalcophanite and todorokite.

The nodules probably formed in a shallow marine oxidizing environment on the western side of the Permian sedimentary basin. The occurrence of an appreciable amount of fluorite in the bed suggests that the water was saline.