cryptomelane

Also known as ebelmenite

Cryptomelane (K(Mn4+,Mn2+)8O16) is the potassium endmember of the hollandite group, a family of tectomanganates with a 2 × 2 tunnel structure.

Key facts

Mineral.name: Cryptomelane
Mineral.image: Kryptomelan2, Maroko.jpg
Mineral.imagesize: 260px
Mineral.category: Oxide mineral
Mineral.formula: K(Mn4+,Mn2+)8O16
Mineral.IMAsymbol: Cml
Mineral.strunz: 4.DK.10
Mineral.system: Tetragonal
Mineral.class: Dipyramidal (4/m) H-M symbol: (4/m)
Mineral.symmetry: I4/m
Mineral.unit cell: a = 9.956 Å, b = 2.8705 Å, c = 9.706 Å; β = 90.95°; Z = 1
Mineral.color: Steel-gray to bluish gray; light tan or gray in reflected light
Mineral.habit: Rare as subhedral crystals, commonly as compact fine-grained masses, banded colloform, botryoidal, or radial fibrous aggregates
Mineral.twinning: Twinning developed on (010) and (101) resulting in a pseudotetragonal unit cell.
Mineral.fracture: Conchoidal
Mineral.tenacity: Brittle
Mineral.mohs: 6 – 6.5
Mineral.luster: Metallic to dull

via Wikipedia infobox

Wikidata facts

Image: Kryptomelan2, Maroko.jpg

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Nickel-Strunz '10th ed', review of (9th ed/ 2009 update): 4.DK.05a
Nickel-Strunz 9th edition (updated 2009): 4.DK.05
Commons category: Cryptomelane
IMA Mineral Symbol: Cml
chemical formula: K(Mn⁴⁺₇Mn³⁺)O₁₆

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Cryptomelane (K(Mn4+,Mn2+)8O16) is the potassium endmember of the hollandite group, a family of tectomanganates with a 2 × 2 tunnel structure.

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.