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 atmosphe ...

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 The oxide mineral class includes those minerals in which the oxide anion (O2−) is bonded to one or more metal alloys. The hydroxide-bearing minerals are typically included in the oxide class. The minerals with complex anion groups such as the si ...

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 X-ray crystallography is the experimental science determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to diffract into many specific directions. By measuring the angles ...

studies of samples from

Tombstone, Arizona Tombstone is a historic city in Cochise County, Arizona, United States, founded in 1877 by prospector Ed Schieffelin in what was then Pima County, Arizona Territory. It became one of the last boomtowns in the American frontier. The town grew si ...

;

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;

Mena, Arkansas Mena ( ) is a city in Polk County, Arkansas, United States. It is also the county seat of Polk County. The population was 5,558 as of the 2020 census. Mena is included in the Ark-La-Tex socio-economic region. Surrounded by the Ouachita National F ...

; 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 constructio ...

.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 Founded in 1958, the International Mineralogical Association (IMA) is an international group of 40 national societies. The goal is to promote the science of mineralogy and to standardize the nomenclature of the 5000 plus known mineral species. Th ...

(IMA). The type locality is the Tombstone District,

Cochise County, Arizona Cochise County () is a county in the southeastern corner of the U.S. state of Arizona. It is named after the Native American chief Cochise. The population was 125,447 at the 2020 census. The county seat is Bisbee and the most populous city is ...

, US. The name comes from the

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for hidden and black, in reference to the confusion and difficulty in recognition of the various black manganese oxide minerals referred to as ''

psilomelane Psilomelane is a group name for hard black manganese oxides including hollandite and romanechite. Psilomelane consists of hydrous manganese oxide with variable amounts of barium and potassium. Psilomelane is erroneously, and uncommonly, known as ...

'', the collective term for hard manganese oxides. It is of rather common occurrence in

oxidized Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a d ...

manganese deposits where it occurs as replacements and open space fillings in

veins Veins are blood vessels in humans and most other animals that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated b ...

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, cal ...

s. It occurs in association with

pyrolusite Pyrolusite is a mineral consisting essentially of manganese dioxide ( Mn O2) and is important as an ore of manganese.. It is a black, amorphous appearing mineral, often with a granular, fibrous, or columnar structure, sometimes forming reniform ...

nsutite Nsutite is a manganese oxide mineral with formula: ( Mn4+1−xMn2+x O2-2x(O H)2x where x = 0.06-0.07).http://www.webmineral.com/data/Nsutite.shtml Webmineral data It is found in most large manganese deposits and was first discovered in Nsuta, Ghan ...

braunite Braunite is a silicate mineral containing both di- and tri- valent manganese with the chemical formula: Mn2+Mn3+6 SiO4 Common impurities include iron, calcium, boron, barium, titanium, aluminium, and magnesium. Braunite forms grey/black tetragon ...

, 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