Hydromagnesite
Encyclopedia
Hydromagnesite is a hydrated magnesium
carbonate mineral with the formula: Mg5(CO3)4(OH)2.4H2O.
It generally occurs associated with the weathering products of magnesium containing minerals such as serpentine or brucite
. It occurs as incrustations and vein or fracture fillings in ultramafic rocks and serpentinite
s. It occurs in hydrothermally altered dolomite
and marble
. It commonly appears in cave
s as speleothem
s and "moonmilk
", deposited from water that has seeped through magnesium rich rocks. It is the most common cave carbonate after calcite
and aragonite
. It thermally decomposes, over a temperature range of approximately 220°C to 550°C, releasing water and carbon dioxide leaving a magnesium oxide residue.
It was first described in 1836 for an occurrence in Hoboken, Hudson County, New Jersey
.
Stromatolite
s in an alkaline (pH
greater than 9) freshwater lake (Salda Gölü
) in southern Turkey
are made of hydromagnesite precipitated by diatom
s and cyanobacteria. Microbial deposition of hydromagnesite is also reported from playa
s in British Columbia
.
as a fire retardant additive for polymers. Hydromagnesite decomposes endothermically, giving off water and carbon dioxide, leaving a magnesium oxide residue. The initial decomposition begins at about 220 °C making it ideal for use as a filler in polymers and giving it certain advantages over the most commonly used fire retardant, aluminium hydroxide
.
Magnesium
Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...
carbonate mineral with the formula: Mg5(CO3)4(OH)2.4H2O.
It generally occurs associated with the weathering products of magnesium containing minerals such as serpentine or brucite
Brucite
Brucite is the mineral form of magnesium hydroxide, with the chemical formula Mg2. It is a common alteration product of periclase in marble; a low-temperature hydrothermal vein mineral in metamorphosed limestones and chlorite schists; and formed during serpentinization of dunites...
. It occurs as incrustations and vein or fracture fillings in ultramafic rocks and serpentinite
Serpentinite
Serpentinite is a rock composed of one or more serpentine group minerals. Minerals in this group are formed by serpentinization, a hydration and metamorphic transformation of ultramafic rock from the Earth's mantle...
s. It occurs in hydrothermally altered dolomite
Dolomite
Dolomite is a carbonate mineral composed of calcium magnesium carbonate CaMg2. The term is also used to describe the sedimentary carbonate rock dolostone....
and marble
Marble
Marble is a metamorphic rock composed of recrystallized carbonate minerals, most commonly calcite or dolomite.Geologists use the term "marble" to refer to metamorphosed limestone; however stonemasons use the term more broadly to encompass unmetamorphosed limestone.Marble is commonly used for...
. It commonly appears in cave
Cave
A cave or cavern is a natural underground space large enough for a human to enter. The term applies to natural cavities some part of which is in total darkness. The word cave also includes smaller spaces like rock shelters, sea caves, and grottos.Speleology is the science of exploration and study...
s as speleothem
Speleothem
A speleothem , commonly known as a cave formation, is a secondary mineral deposit formed in a cave. Speleothems are typically formed in limestone or dolostone solutional caves.-Origin and composition:...
s and "moonmilk
Moonmilk
Moonmilk is a white, creamy substance found inside caves. It is similar to other deposits, but its unique quality is that it does not harden or turn to stone...
", deposited from water that has seeped through magnesium rich rocks. It is the most common cave carbonate after calcite
Calcite
Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate . The other polymorphs are the minerals aragonite and vaterite. Aragonite will change to calcite at 380-470°C, and vaterite is even less stable.-Properties:...
and aragonite
Aragonite
Aragonite is a carbonate mineral, one of the two common, naturally occurring, crystal forms of calcium carbonate, CaCO3...
. It thermally decomposes, over a temperature range of approximately 220°C to 550°C, releasing water and carbon dioxide leaving a magnesium oxide residue.
It was first described in 1836 for an occurrence in Hoboken, Hudson County, New Jersey
Hudson County, New Jersey
Hudson County is the smallest county in New Jersey and one of the most densely populated in United States. It takes its name from the Hudson River, which creates part of its eastern border. Part of the New York metropolitan area, its county seat and largest city is Jersey City.- Municipalities...
.
Stromatolite
Stromatolite
Stromatolites or stromatoliths are layered accretionary structures formed in shallow water by the trapping, binding and cementation of sedimentary grains by biofilms of microorganisms, especially cyanobacteria ....
s in an alkaline (pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...
greater than 9) freshwater lake (Salda Gölü
Lake Salda
Lake Salda is a mid-size crater lake in southwestern Turkey, within the boundaries of Yeşilova district depending Burdur Province, and it lies at a distance of about fifty kilometers to the west from the province seat of Burdur....
) in southern Turkey
Turkey
Turkey , known officially as the Republic of Turkey , is a Eurasian country located in Western Asia and in East Thrace in Southeastern Europe...
are made of hydromagnesite precipitated by diatom
Diatom
Diatoms are a major group of algae, and are one of the most common types of phytoplankton. Most diatoms are unicellular, although they can exist as colonies in the shape of filaments or ribbons , fans , zigzags , or stellate colonies . Diatoms are producers within the food chain...
s and cyanobacteria. Microbial deposition of hydromagnesite is also reported from playa
Dry lake
Dry lakes are ephemeral lakebeds, or a remnant of an endorheic lake. Such flats consist of fine-grained sediments infused with alkali salts. Dry lakes are also referred to as alkali flats, sabkhas, playas or mud flats...
s in British Columbia
British Columbia
British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...
.
Uses
Its most common industrial use is as a mixture with huntiteHuntite
Huntite is a carbonate mineral with the chemical formula Mg3Ca4.It often occurs in combination with hydromagnesite.It thermally decomposes over a temperature range of about 450–800 °C, releasing carbon dioxide and leaving a residue of magnesium oxide and calcium oxide.-Uses:Its most common...
as a fire retardant additive for polymers. Hydromagnesite decomposes endothermically, giving off water and carbon dioxide, leaving a magnesium oxide residue. The initial decomposition begins at about 220 °C making it ideal for use as a filler in polymers and giving it certain advantages over the most commonly used fire retardant, aluminium hydroxide
Aluminium hydroxide
Aluminium hydroxide, Al3, ATH, sometimes erroneously called Hydrate of alumina, is found in nature as the mineral gibbsite and its three, much more rare forms, polymorphs: bayerite, doyleite and nordstrandite. Closely related are aluminium oxide hydroxide, AlO, and aluminium oxide, Al2O3,...
.