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PSILOMELANE

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Originally appearing in Volume V22, Page 542 of the 1911 Encyclopedia Britannica.
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PSILOMELANE , a See also:

mineral consisting of hydrous See also:manganese See also:oxide with variable amounts of See also:barium, See also:potassium, &c. It is sometimes considered to be a hydrous manganese manganate, but of doubtful See also:composition. The amount of manganese See also:present corresponds to 7o-8o% of manganous oxide with 10-15% of " available " See also:oxygen. The mineral is amorphous and occurs as botryoidal and stalactitic masses with a smooth shining See also:surface and submetallic lustre. The name has reference to this characteristic See also:appearance, being from the See also:Greek >GtXbs (naked, smooth) and µfXas (See also:black); a Latinized See also:form is calvonigrite, and a See also:German name with the same meaning is Schwarzer Glaskopf. Psilomelane is readily distinguished from other hydrous manganese oxides (See also:manganite and See also:wad) by its greater hardness (H. = 5 2) ; the sp. gr. 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 See also:iron hydrates. It is soluble in hydrochloric See also:acid with See also:evolution of See also:chlorine. It is a See also:common and important ore of manganese, occurring under the same conditions and having the same commercial applications as pyrolusite (q.v.). It is found at many localities; amongst those which have yielded typical botryoidal specimens may be mentioned the Restormel iron mine at See also:Lostwithiel in See also:Cornwall, Brendon See also:Hill in See also:Somerset, by in th9 Orkneys, Sayn near See also:Coblenz, and Crimora in See also:Augusta See also:county, See also:Virginia.

With pyrolusite it is extensively See also:

mined in See also:Vermont, Virginia, See also:Arkansas and Nova See also:Scotia.

End of Article: PSILOMELANE

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