Cryptomelane is a

potassium Potassium is the chemical element with the symbol K (from Neo-Latin ''kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmosph ...

manganese Manganese is a chemical element with the symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese is a transition metal with a multifaceted array of industrial alloy use ...

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; Mena, Arkansas; and

Philipsburg, Montana Philipsburg is a town in and the county seat of Granite County, Montana, United States. The population was 841 at the 2020 census. The town was named after the famous mining engineer Philip Deidesheimer, who designed and supervised the construct ...

.Richmond, W. E., and Fleischer, M., ''Cryptomelane, a new name for the commonest of the "psilomelane" minerals,'' American Mineralogist, 27, 607, 1942
/ref> Cryptomelane was approved in 1982 by the International Mineralogical Association (IMA). The type locality is the Tombstone District, Cochise County, Arizona, US. The name comes from the

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

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

vug A vug, vugh, or vugg ( ) is a small- to medium-sized cavity inside rock. It may be formed through a variety of processes. Most commonly, cracks and fissures opened by tectonic activity (folding and faulting) are partially filled by quartz, ...

s. It occurs in association with pyrolusite, nsutite,

braunite Braunite is a silicate mineral containing both di- and tri-Valence (chemistry), valent manganese with the chemical formula: Mn2+Mn3+6 8, SiO4 Common impurities include iron, calcium, boron, barium, titanium, aluminium, and magnesium. Braunite ...

, chalcophanite,

manganite Manganite is a mineral composed of manganese oxide-hydroxide, MnO(OH), crystallizing in the monoclinic system (pseudo-orthorhombic). Crystals of manganite are prismatic and deeply striated parallel to their length; they are often grouped togethe ...

and various other manganese oxides.

References

Manganese(II,IV) minerals Oxide minerals Tetragonal minerals Minerals in space group 87 {{oxide-mineral-stub