Cryptomelane is a potassium oxide mineral with formula K(Mn4+,Mn2+)8O16.
In 1942 the name cryptomelane was proposed as part of an effort to sort out the manganese oxide minerals referred to as psilomelane. Cryptomelane was identified and defined based on X-ray diffraction studies of samples from Tombstone, Arizona; Deming, New Mexico ; and Philipsburg, Montana
Cryptomelane was approved in 1982 by the International Mineralogical Association (IMA). The type locality, Cochise County, Arizona , US. The name comes from the Greek for hidden and black, in reference to the confusion and difficulty in recognition of the various black manganese oxide minerals referred to as psilomelane , the collective term for hard manganese oxides.
It is of rather common occurrence in oxidized manganese deposits where it occurs as replacements and open space fillings in veins and vugs , nsutite , manganite