Psilomelane

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Psilomelane

Psilomelane, also known as black hematite, is a group name for hard black manganese oxide

Manganese oxide

Manganese oxide is a generic term used to describe a variety of manganese oxides and hydroxides. It may refer to:* Manganese oxide, MnO* Manganese oxide, Mn3O4...
s such as hollandite and romanechite

Romanèchite

Roman?chite is the primary constituent of psilomelane, which is a mixture of minerals. Most psilomelane is not pure romanechite, so it is incorrect to consider them synonyms....
. Psilomelane consists of hydrous manganese

Manganese

Manganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a Oxidation state in nature , and in many minerals....
oxide with variable amounts of barium

Barium

Barium is a chemical element. It has the symbol Ba, and atomic number 56. Barium is a soft silvery metallic alkaline earth metal. It is never found in nature in its pure form due to its reactivity with Earth's atmosphere....
and potassium

Potassium

Potassium is a chemical element. It has the symbol K , atomic number 19, and atomic mass 39.0983. Potassium was first isolated from potash, hence the name....
.

ralized formula may be represented as Ba(Mn²⁺)(Mn⁴⁺)₈O₁₆(OH)₄ or as (Ba,H₂O)₂Mn₅O₁₀.

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Encyclopedia

Psilomelane, also known as black hematite, is a group name for hard black manganese oxide

Manganese oxide

Romanèchite

Manganese

Barium

Potassium

Potassium is a chemical element. It has the symbol K , atomic number 19, and atomic mass 39.0983. Potassium was first isolated from potash, hence the name....
.

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

Oxygen

Oxygen no O2 produced; 2) O2 produced, but absorbed in oceans & seabed rock; 3) O2 starts to gas out of the oceans, but is absorbed by land surfaces and formation of ozone layer; 4-5) O2 sinks filled and the gas accumulates]]...
.

Characteristics

Psilomelane is amorphous and occurs as botryoidal and stalactitic masses with a smooth shining surface and submetallic lustre. The mineral

Mineral

A mineral is a naturally occurring solid formed through Geology processes that has a characteristic chemical composition, a highly ordered atomic structure, and specific physical properties....
is readily distinguished from other hydrous manganese oxides (manganite and wad) by its greater hardness

Mohs scale of mineral hardness

Not to be confused with Siemens_#Mho, a unit of electric conductance.The Mohs scale of mineral hardness characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer material....
5 to 6; the specific gravity

Specific gravity

Specific gravity is defined as the ratio of the density of a given solid or liquid substance to the density of water at a specific temperature and pressure, typically at 4?C and , making it a dimensionless quantity ....
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

Hydrochloric acid

Hydrochloric acid is the solution of hydrogen chloride in water. It is a highly corrosive, strong acid mineral acid and has major industrial uses....
with evolution of chlorine

Chlorine

Chlorine...
gas.

History and occurrence

The name has reference to this characteristic appearance, from the Greek

Greek language

Greek is an Indo-European languages native to the southern Balkan peninsula, the language of the Greek people. It forms an independent branch within Indo-European....
for (naked, smooth) and (black); a Latin

Latin

Latin is an Italic language, historically spoken in Latium and Ancient Rome. Through the Military history of the Roman Empire, Latin spread throughout the Mediterranean and a large part of Europe....
ized form is calvonigrite, and a German

German language

German is a West Germanic languages, thus related to and classified alongside English language and Dutch language. It is one of the world's world language and the most widely spoken mother tongue in the European Union....
name with the same meaning is Schwarzer Glaskopf. It is a common and important ore

Ore

An ore is a type of Rock that contains minerals such as gemstones and metals that can be extracted through mining and refined for use. Samples of ore in the form of exceptionally beautiful crystals, exotic layering visible when sectioned or polished or metallic presentations such as large nuggets or crystalline formations of metals suc...
of manganese, occurring under the same conditions and having the same commercial applications as pyrolusite

Pyrolusite

Pyrolusite is a mineral consisting essentially of manganese dioxide and is important as an ore of manganese. It is a soft, black, amorphous appearing mineral, often with a granular, fibrous or columnar structure, sometimes forming reniform crusts....
. It is found at many localities; amongst those which have yielded typical botryoidal specimens may be mentioned the Restormel iron mine at Lostwithiel

Lostwithiel

Lostwithiel is a civil parish and small town in Cornwall, England, United Kingdom at the head of the estuary of the River Fowey. According to the 2001 census it had a population of 2,739....
in Cornwall

Cornwall

Cornwall , constitutional Duchy and palatine, is a metropolitan and non-metropolitan counties of England of England, United Kingdom, located at the tip of the south-western peninsula of Great Britain....
, Brendon Hills

Brendon Hills

The Brendon Hills are composed of a lofty ridge of hills in the west of Somerset, England. The terrain is broken by a series of deeply incised streams and rivers running roughly southwards to meet the River Haddeo, a tributary of the River Exe....
in Somerset

Somerset

Somerset is a Counties of England in South West England. The county town is Taunton, which is in the south of the county. The Ceremonial counties of England of Somerset borders the counties of Bristol and Gloucestershire to the north, Wiltshire to the east, Dorset to the south-east, and Devon to the south-west....
, Hoy

Hoy

Hoy is one of the Orkney Islands in Scotland. With an area of , it is the second largest of the Orkney Islands after the Orkney Mainland. It is connected by a southern causeway called The Ayre to South Walls....
in Orkney, Sayn near Coblenz, and Crimora in Augusta county, Virginia. With pyrolusite it is extensively mined in Vermont

Vermont

Vermont is a U.S. state in the New England region of the Northeastern United States United States. The state ranks 43rd by land area, , and 45th by total area....
, Virginia

Virginia

The Commonwealth of Virginia is an United States U.S. state on the East Coast of the United States of the Southern United States. The state is known as the "Old Dominion" and sometimes as "Mother of Presidents", because it is the birthplace of Lists of United States Presidents by place of birth#By state....
, Arkansas

Arkansas

Arkansas is a U.S. state located in the Southern United States of the United States. Arkansas shares a border with six states, with its eastern border largely defined by the Mississippi River....
, and Nova Scotia

Nova Scotia

Nova Scotia is a Canadian Provinces and territories of Canada located on Canada's southeastern coast. It is the most populous province in Atlantic Canada....
.

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