PSILOMELANE MINERAL FACTS Nevada Turquoise gem stones
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Psilomelane Mineral Facts:

Chemical Formula: (Ba,H2O)2Mn5O10
Psilomelane is probably a mixture of colloidal oxides and hydroxides of manganese in various proportions. In most specimens there is a notable percentage of Barium or potassium oxides present, and in others small quantities of lithium and thallium can be found

Colors: Black.
Its streak is Brownish black.

Hardness: 5.5 to 6

Density: 4.2

Cleavage: None.

Crystallography: Monoclinic
The mineral occurs in globular, botryoidal, stalactitic, and massive forms exhibiting, in many instances, an obscure fibrous structure.

Luster: Dull and earthy to submetallic. It is opaque. 



Composition, Structure and Associated Minerals:
Psilomelane occurs in veins associated with pyrolusite and other manganese compounds, as nodules in clay beds, and as coatings on many manganiferous minerals. In all essentially cases it is probably a product of weathering of other manganese bearing minerals. The name is from the Greek, meaning smooth black, ie., psilos, smooth, and melas, black

Identification and Diagnostics
Psilomelane is infusible before the blowpipe, in some cases coloring the flame green (because of the Barium present) and in others violet (for potassium). With fluxes it reacts for manganese. A small amount of mineral fused in an oxidizing flame with sodium carbonate gives an opaque bluish green bead. Borax bead test gives the same results as with pyrolusite. In the closed tube it yields much water. It is soluble in HC1with evolution of chlorine gas. It is distinguished from most other manganese oxides and hydroxides by its greater hardness.

Botryoidal Psilomelane Aggregate

Botryoidal Psilomelane Aggregate

Occurrence, Localities and Origins:
Psilomelane is of an uncertain composition, chiefly manganese oxides, MnO2 with MnO and H2O, also small amounts of barium oxide, cobalt oxide, potassium oxide, etc. The barium and potassium components are thought to have been absorbed from the secondary solutions with formed the mineral. It is basically
amorphous or non-crystalline, forming massive, botryoidal, or stalactitic deposits.  It is an important manganese ore, occurring usually with othyer manganese minerals, especially with pyrolusite.

Psilomelane localities: It is found in large quantity at Elgersburg in Thyringia; at Ilfeld, Harz; and at various places in Saxony. In the United States it occurs with pyrolusite and other ores of manganese at Brandon, Vermont; in the James River Valley, and the Blue Ridge region of Virginia; in northeastern Tennessee; at Cartersville, Georgia; at Batesville, Arkansas; and in a stretch of country about forty miles southeast of San Francisco, California. At many of these points it has been mined as an ore of manganese.

Wad is a soft, earthy, black or dark brown aggregate of manganese compounds closely related to psilomelane. It also occurs in globular, botryoidal, stalactitic, flaky and porous masses, which, in some cases, are so light that they float on water. Like Psilomelane, it also occurs in fairly compact layers and coats the surfaces of cracks, often forming branching stains, known as dendrites. Wad contains more water than psilomelane, of which it appears often to be a decomposition product. More frequently it results from the weathering of manganiferous iron carbonate. It is particularly abundant in the oxidized portions of veins containing manganese carbonates and silicates. Wad is easily distinguished from all other soft black minerals, except pyrolusite, by the reaction for manganese, and from all other manganese compounds, except pyrolusite, by its softness. From pyrolusite it is distinguished by its content of water.  It occurs in most of the localities at which other manganese compounds are found and is mined as an ore of manganese along with the rest of these minerals. 

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Please note that the author, Chris Ralph, retains all copyrights to this entire document and it may not be reproduced, quoted or copied without permission.

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