Birnessite
Encyclopedia
Birnessite(Mn4+,Mn3+)2O4 · 1.5 H2O is an oxide mineral
of manganese
along with calcium
, potassium
and sodium
. It has a dark brown to black color with a submetallic luster
. It is also very soft, with a Mohs hardness of 1.5. Birnessite is formed by precipitation
in lake
s, ocean
s and groundwater
and is a major component of desert varnish
and deep sea manganese nodule
s.
, Scotland
. Birnessite is found as an oxidation product of several other minerals, including rhodonite
, rhodochrosite
, and as a weathering product of franklinite-wilminite ore. It has also been found as a coating along joint planes and fractures within a trachyte
sill
. However, it has been most commonly seen as a constituent of oceanic nodules of manganese
.
A recent study found that the mineral is able to break down prions via oxidation. How well this process works outside the laboratory is unclear.
, Mexico
, while other notations have been made in Canada
, at Cummington, Massachusetts
, from the aforementioned nodules in both the Atlantic and Pacific Oceans, from the Tachaki Mine in Japan
, the Treburland Mine in Cornwall
, England
, and from a bog
in Norway
.
that contains a high proportion of manganese
. While natural forms generally contain foreign ions (i.e. Na
, Ca
, K
) they are considered non-essential and synthetic forms of the mineral
can be produced without them. However, most of the synthetic versions of the mineral undergo significant water loss at temperatures below 100ºC. Its structure is thought to be similar to that of chalcophanite, and has been modeled as such by Burns. The structure itself consists of sheets of water molecules found between sheets of edge-sharing molecules of MnO6 octahedra, and repeated on an average of every 7.2 Å
, doing so along the c-axis. Of the six octahedral sites in the MnO6 octahedral layer, one is left unoccupied; Mn2+ and Mn3+ lie above each vacant slot on the octahedral. These Mn
ions are low-valence
, and associate with O, in both the octahedral and in the water sheets.
Oxide mineral
The oxide mineral class includes those minerals in which the oxide anion is bonded to one or more metal ions. The hydroxide bearing minerals are typically included in the oxide class...
of manganese
Manganese
Manganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature , and in many minerals...
along with calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
, potassium
Potassium
Potassium is the chemical element with the symbol K and atomic number 19. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction.Potassium and sodium are...
and sodium
Sodium
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...
. It has a dark brown to black color with a submetallic luster
Lustre (mineralogy)
Lustre is a description of the way light interacts with the surface of a crystal, rock, or mineral. The word lustre traces its origins back to the Latin word lux, meaning "light", and generally implies radiance, gloss, or brilliance....
. It is also very soft, with a Mohs hardness of 1.5. Birnessite is formed by precipitation
Precipitation (chemistry)
Precipitation is the formation of a solid in a solution or inside anothersolid during a chemical reaction or by diffusion in a solid. When the reaction occurs in a liquid, the solid formed is called the precipitate, or when compacted by a centrifuge, a pellet. The liquid remaining above the solid...
in lake
Lake
A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...
s, ocean
Ocean
An ocean is a major body of saline water, and a principal component of the hydrosphere. Approximately 71% of the Earth's surface is covered by ocean, a continuous body of water that is customarily divided into several principal oceans and smaller seas.More than half of this area is over 3,000...
s and groundwater
Groundwater
Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of rock formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock...
and is a major component of desert varnish
Desert varnish
Desert varnish, or rock varnish is a orange-yellow to black coating found on exposed rock surfaces in arid environments. Desert varnish is usually around one micron thick and present nanometre-scale layering...
and deep sea manganese nodule
Manganese nodule
Polymetallic nodules, also called manganese nodules, are rock concretions on the sea bottom formed of concentric layers of iron and manganese hydroxides around a core. The core may be microscopically small and is sometimes completely transformed into manganese minerals by crystallization...
s.
History
It was first described in 1956 and named for an occurrence in Birness, AberdeenshireAberdeenshire
Aberdeenshire is one of the 32 unitary council areas in Scotland and a lieutenancy area.The present day Aberdeenshire council area does not include the City of Aberdeen, now a separate council area, from which its name derives. Together, the modern council area and the city formed historic...
, Scotland
Scotland
Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...
. Birnessite is found as an oxidation product of several other minerals, including rhodonite
Rhodonite
Rhodonite is a manganese inosilicate, SiO3 and member of the pyroxenoid group of minerals, crystallizing in the triclinic system...
, rhodochrosite
Rhodochrosite
Rhodochrosite is a manganese carbonate mineral with chemical composition MnCO3. In its pure form, it is typically a rose-red color, but impure specimens can be shades of pink to pale brown. The streak is white. Its Mohs hardness varies between 3.5 and 4. Its specific gravity is 3.5 to 3.7. It...
, and as a weathering product of franklinite-wilminite ore. It has also been found as a coating along joint planes and fractures within a trachyte
Trachyte
Trachyte is an igneous volcanic rock with an aphanitic to porphyritic texture. The mineral assemblage consists of essential alkali feldspar; relatively minor plagioclase and quartz or a feldspathoid such as nepheline may also be present....
sill
Sill (geology)
In geology, a sill is a tabular sheet intrusion that has intruded between older layers of sedimentary rock, beds of volcanic lava or tuff, or even along the direction of foliation in metamorphic rock. The term sill is synonymous with concordant intrusive sheet...
. However, it has been most commonly seen as a constituent of oceanic nodules of manganese
Manganese
Manganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature , and in many minerals...
.
A recent study found that the mineral is able to break down prions via oxidation. How well this process works outside the laboratory is unclear.
Geologic occurrence
Levinson noted the presence of Birnessite in one or more mines from the region around ZacatecasZacatecas
Zacatecas officially Estado Libre y Soberano de Zacatecas is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 58 municipalities and its capital city is Zacatecas....
, Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
, while other notations have been made in Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
, at Cummington, Massachusetts
Massachusetts
The Commonwealth of Massachusetts is a state in the New England region of the northeastern United States of America. It is bordered by Rhode Island and Connecticut to the south, New York to the west, and Vermont and New Hampshire to the north; at its east lies the Atlantic Ocean. As of the 2010...
, from the aforementioned nodules in both the Atlantic and Pacific Oceans, from the Tachaki Mine in Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
, the Treburland Mine in Cornwall
Cornwall
Cornwall is a unitary authority and ceremonial county of England, within the United Kingdom. It is bordered to the north and west by the Celtic Sea, to the south by the English Channel, and to the east by the county of Devon, over the River Tamar. Cornwall has a population of , and covers an area of...
, England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
, and from a bog
Bog
A bog, quagmire or mire is a wetland that accumulates acidic peat, a deposit of dead plant material—often mosses or, in Arctic climates, lichens....
in Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...
.
Composition and structure
Birnessite is a phyllomanganate, which is a type of ferroalloyFerroalloy
Ferroalloy refers to various alloys of iron with a high proportion of one or more other element, manganese or silicon for example. It is used in the production of steels and alloys as a raw material.The main ferroalloys are:*FeAl – ferroaluminum...
that contains a high proportion of manganese
Manganese
Manganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature , and in many minerals...
. While natural forms generally contain foreign ions (i.e. Na
Sodium
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...
, Ca
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
, K
K
K is the eleventh letter of the English and basic modern Latin alphabet.-History and usage:In English, the letter K usually represents the voiceless velar plosive; this sound is also transcribed by in the International Phonetic Alphabet and X-SAMPA....
) they are considered non-essential and synthetic forms of the mineral
Mineral
A mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...
can be produced without them. However, most of the synthetic versions of the mineral undergo significant water loss at temperatures below 100ºC. Its structure is thought to be similar to that of chalcophanite, and has been modeled as such by Burns. The structure itself consists of sheets of water molecules found between sheets of edge-sharing molecules of MnO6 octahedra, and repeated on an average of every 7.2 Å
Ångström
The angstrom or ångström, is a unit of length equal to 1/10,000,000,000 of a meter . Its symbol is the Swedish letter Å....
, doing so along the c-axis. Of the six octahedral sites in the MnO6 octahedral layer, one is left unoccupied; Mn2+ and Mn3+ lie above each vacant slot on the octahedral. These Mn
Manganese
Manganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature , and in many minerals...
ions are low-valence
Valence (chemistry)
In chemistry, valence, also known as valency or valence number, is a measure of the number of bonds formed by an atom of a given element. "Valence" can be defined as the number of valence bonds...
, and associate with O, in both the octahedral and in the water sheets.