From Surf Wiki (app.surf) — the open knowledge base

Psilomelane

Hard black manganese oxides (romanechite, mainly)

Field	Value
name	Psilomelane
category	Oxide minerals
image	Mineraly.sk - psilomelan.jpg
imagesize	260px
formula	General formula:
, or as
Barium manganese oxide hydroxide
molweight	590.03 g/mol
system	Monoclinic
color	Black with gray pyrolusite bands
habit	Botryoidal, mammillary, reniform
cleavage	None
fracture	Conchoidal and uneven
mohs	5.0 – 6.0
luster	Sub-metallic, dull
polish	Vitreous to subadamantine
streak	Brownish black
gravity	3.7 – 4.7
solubility	in hydrochloric acid
diaphaneity	Opaque
other	Hard black manganese oxides such as hollandite and romanechite

, or as Barium manganese oxide hydroxide

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 black hematite, despite not being related to true hematite, which is an iron oxide.

Formula

Generalized formula may be represented as or as . 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 has no definite chemical composition 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. 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, dating back to 1758, makes reference to its characteristic appearance, from the ancient Greek ψιλός: psilos for (naked, smooth, bald) and μέλας: melas (black); a Latinized form is calvonigrite from calvo for (bald, smooth) and negri (black).

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, Hout Bay near Cape Town, and Crimora in Augusta county, Virginia. With pyrolusite it is extensively mined in Vermont, Virginia, Arkansas, and Nova Scotia.

Image gallery

File:Psilomelane-167850.jpg|A specimen of manganese oxide File:Psilomelane-dendrites.jpg|Dendritic psilomelane on a cobble File:Psilomelane+Hausmanite.jpg|Slab of manganese ore showing a mixture of hausmannite and psilomelane in a zonal arrangement and a radiating mass of white barite at the center File:Psilomelane-pyrolusite 7100.4947.jpg|Psilomelane and pyrolusite from Solnhofen Limestone quarries, Solnhofen, Franconia, Bavaria, Germany File:Vanadinite-Psilomelane-112809.jpg|Vanadinite and psilomelane from Taouz, Er Rachidia Province, Meknès-Tafilalet Region, Morocco

References

Info: Wikipedia Source

This article was imported from Wikipedia and is available under the Creative Commons Attribution-ShareAlike 4.0 License. Content has been adapted to SurfDoc format. Original contributors can be found on the article history page.

barium-minerals manganese(ii,iv)-minerals oxide-minerals monoclinic-minerals

Want to explore this topic further?

Ask Mako anything about Psilomelane — get instant answers, deeper analysis, and related topics.

Research with Mako

Free with your Surf account

Content sourced from Wikipedia, available under CC BY-SA 4.0.

This content may have been generated or modified by AI. CloudSurf Software LLC is not responsible for the accuracy, completeness, or reliability of AI-generated content. Always verify important information from primary sources.

Report