Psilomelane


Psilomelane

Infobox mineral
name = Psilomelane
category =
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caption = A native sample of psilomelane
formula = The general formula
Ba(Mn2+)(Mn4+)8O16(OH)4 or as (Ba,H2O)2Mn5O10
Barium Manganese Oxide Hydroxide
molweight = 590.03 gm
color = black with gray pyrolusite bands
habit = Botryoidal, Mammillary, Reniform
system = monoclinic
twinning =
cleavage = none
fracture = conchoidal and uneven
mohs = 5.0 - 6.0
luster = Sub-Metallic, Dull
polish = vitreous to subadamantine
refractive =
opticalprop =
birefringence =
pleochroism =
streak = brownish black
gravity = 3.7 - 4.7
melt =
fusibility =
diagnostic =
solubility = in hydrochloric acid
diaphaneity = Opaque
other = hard black manganese oxides such as hollandite and romanechite
var1 =
var2 =
var3 =
var4 =
var5 =
var6 =

Psilomelane, also known as black hematite, is a group name for hard black manganese oxides such as hollandite and romanechite. Psilomelane consists of hydrous manganese oxide with variable amounts of barium and potassium.

Formula

Generalized formula may be represented as Ba(Mn2+)(Mn4+)8O16(OH)4 or as (Ba,H2O)2Mn5O10. It is sometimes considered to be a hydrous manganese manganate, but of doubtful composition. The amount of manganese present corresponds to 70-80% of manganous oxide with 10-15% of available oxygen.

Characteristics

Psilomelane is amorphous and occurs as botryoidal and stalactitic masses with a smooth shining surface and submetallic lustre. The mineral is readily distinguished from other hydrous manganese oxides (manganite and wad) by its greater hardness 5 to 6; the specific gravity varies from 3.7 to 4.7. The streak is brownish black and the fracture smooth. Owing to its amorphous nature, the mineral often contains admixed impurities, such as iron hydroxides. It is soluble in hydrochloric acid with evolution of chlorine gas.

History and occurrence

The name has reference to this characteristic appearance, from the Greek for (naked, smooth) and (black); a Latinized form is calvonigrite, and a German name with the same meaning is Schwarzer Glaskopf. It is a common and important ore of manganese, occurring under the same conditions and having the same commercial applications as pyrolusite. It is found at many localities; amongst those which have yielded typical botryoidal specimens may be mentioned the Restormel iron mine at Lostwithiel in Cornwall, Brendon Hills in Somerset, Hoy in Orkney, Sayn near Coblenz, and Crimora in Augusta county, Virginia. With pyrolusite it is extensively mined in Vermont, Virginia, Arkansas, and Nova Scotia.

Psilomelane is also cut, shaped, and polished for a variety of jewelry applications.

References

*1911
* [http://www.mindat.org/show.php?id=3304&ld=1&pho= Mindat with locality data]
* [http://webmineral.com/data/Psilomelane.shtml Webmineral]
* [http://mineral.galleries.com/minerals/oxides/psilomel/psilomel.htm Mineral galleries]


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Look at other dictionaries:

  • PSILOMÉLANE — Oxyde hydraté naturel de manganèse observé généralement en concrétions à structures en zones concentriques ou en agrégats microcristallins (les enduits dendritiques sont fréquents). Le psilomélane est noir à l’éclat submétallique. La dureté (4 6) …   Encyclopédie Universelle

  • Psilomelane — Psi*lom e*lane, n. [Gr. ? bare + ?, ?, black.] (Min.) A hydrous oxide of manganese, occurring in smooth, botryoidal forms, and massive, and having an iron black or steel gray color. [1913 Webster] …   The Collaborative International Dictionary of English

  • psilomelane — /suy lom euh layn /, n. a common mineral consisting of a mixture of pyrolusite and other oxides of manganese, usually found in black, rounded masses: an ore of manganese. [1825 35; < Gk psiló(s) bare, smooth + mélan, neut. of mélas black] * * *… …   Universalium

  • psilomelane — psilomelanas statusas T sritis chemija apibrėžtis Mineralas. formulė mMnO·MnO₂·nH₂O atitikmenys: angl. psilomelane rus. псиломелан …   Chemijos terminų aiškinamasis žodynas

  • psilomelane — noun Any hard, black hydrous manganese oxide with variable amounts of barium and potassium …   Wiktionary

  • psilomélane — (psi lo mé la n ) s. m. Sorte d oxyde de manganèse naturel …   Dictionnaire de la Langue Française d'Émile Littré

  • psilomelane — psi·lo·mel·ane …   English syllables

  • psilomelane — /saɪloʊˈmɛleɪn/ (say suyloh melayn) noun 1. a common mineral, a hydrated barium manganate, occurring in smooth, black to steel grey, botryoidal or stalactitic forms and in masses; an ore of manganese. 2. any hard massive manganese oxide. {Greek… …   Australian English dictionary

  • psilomelane — noun a mineral consisting of hydrated basic oxide of manganese and barium; a source of manganese • Hypernyms: ↑mineral • Substance Meronyms: ↑manganese, ↑Mn, ↑atomic number 25 …   Useful english dictionary

  • Manganese — Not to be confused with Magnesium. This article is about the chemical element. For the ghost town, see Manganese, Minnesota. For the steamship, see SS Manganese. chromium ← manganese → iron ↑ Mn ↓ Tc …   Wikipedia