Messelite is a mineral with formula Ca₂(Fe²⁺,Mn²⁺)(PO₄)₂·2H₂O. It was discovered in Germany and described in 1890. The mineral was subsequently discredited in 1940, reinstated and named ''neomesselite'' in 1955, and the name restored to ''messelite'' in 1959.

Description

Messelite is a translucent mineral that is white, pale greenish white, greenish gray, pink, or colorless. The mineral may be granular or occur as internally radial aggregates of

lamellar A ''lamella'' (plural ''lamellae'') is a small plate or flake, from the Latin, and may also be used to refer to collections of fine sheets of material held adjacent to one another, in a gill-shaped structure, often with fluid in between though s ...

crystals arranged as globes, hemispheres, or sheafs, up to . Messelite is a member of the fairfieldite group.

History

Messelite was discovered in Messel,

Hesse Hesse (, , ) or Hessia (, ; german: Hessen ), officially the State of Hessen (german: links=no, Land Hessen), is a state in Germany. Its capital city is Wiesbaden, and the largest urban area is Frankfurt. Two other major historic cities are Dar ...

, Germany, by a Dr. Spiegel who worked as technical director at a local factory. The specimen contained a number of crystals associated with

carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon mak ...

aceous material. It did not conform to any known mineral at the time, a fact confirmed when it was studied at a local mineralogical institute. The mineral was described by W. Muthmann in 1890 in the journal ''Zeitschrift für Kristallographie'' and its formula was identified as (Ca²⁺,Fe²⁺,Mn²⁺)₃(PO₄)₂·H₂O. At the request of Dr. Spiegel, the mineral was named ''messelite'' (german: Messelit) after the area in which it was discovered. The first reevaluation of messelite was carried out by C. W. Wolfe in 1940. Wolfe concluded that the material was anapaite partially altered to collinsite and he discredited messelite as a valid mineral species. Later, an unaltered mineral was found with the formula (Ca²⁺,Fe²⁺,Mn²⁺)₃(PO₄)₂·2H₂O, essentially identical to the formula of messelite reported by Muthmann. It was analyzed by Clifford Frondel and found to be the disordered iron-rich analogue of fairfieldite. Frondel proposed in 1955 that the mineral be named ''neomesselite''. A few years later, additional material was obtained from the type locality of Messel and studied with optical and x-ray methods. The specimen was determined to consist primarily of material identical to the neomesselite described by Frondel with a rim of anapaite. Since it is likely that the mixture studied by Muthmann was primarily this mineral, it was decided around 1959 that the name ''neomesselite'' should be discarded in favor of ''messelite''. When the IMA was founded, messelite was

grandfathered A grandfather clause, also known as grandfather policy, grandfathering, or grandfathered in, is a provision in which an old rule continues to apply to some existing situations while a new rule will apply to all future cases. Those exempt from t ...

as a valid mineral species.

Occurrence

Messelite has been found in Austria, Brazil, Canada, Czech Republic, France, Germany, Japan, Kazakhstan, Spain, Sweden, Switzerland, Ukraine, and the United States. The mineral tends to form in granite pegmatites by

hydrothermal alteration Metasomatism (from the Greek μετά ''metá'' "change" and σῶμα ''sôma'' "body") is the chemical alteration of a rock by hydrothermal and other fluids. It is the replacement of one rock by another of different mineralogical and chemical co ...

at a late stage. Messelite occurs in association with

amblygonite Amblygonite () is a fluorophosphate mineral, , composed of lithium, sodium, aluminium, phosphate, fluoride and hydroxide. The mineral occurs in pegmatite deposits and is easily mistaken for albite and other feldspars. Its density, cleavage and ...

, anapaite,

brazilianite Brazilianite, whose name derives from its country of origin, Brazil, is a typically yellow-green phosphate mineral, most commonly found in phosphate-rich pegmatites. It occurs in the form of perfect crystals grouped in druses, in pegmatites, and ...

, eosphorite, fairfieldite, goyazite, graftonite,

herderite Herderite is a phosphate mineral belonging to the apatite, phosphate group, with formula CaBe(PO4)(F,OH). It forms monoclinic crystals, often twinned and variable in colour from colourless through yellow to green. It forms a series with the more ...

, hureaulite, ludlamite, phosphoferrite,

siderite Siderite is a mineral composed of iron(II) carbonate (FeCO3). It takes its name from the Greek word σίδηρος ''sideros,'' "iron". It is a valuable iron mineral, since it is 48% iron and contains no sulfur or phosphorus. Zinc, magnesium and ...

triphylite Triphylite is a lithium iron(II) phosphate mineral with the chemical formula LiFePO4.IMA-CNMNC List of Miner ...

vivianite Vivianite () is a hydrated iron phosphate mineral found in a number of geological environments. Small amounts of manganese Mn2+, magnesium Mg and calcium Ca may substitute for iron Fe2+ in the structure.Gaines et al (1997) Dana’s New Minera ...

, and

whitlockite Whitlockite is a mineral, an unusual form of Tricalcium phosphate, calcium phosphate. Its formula is Ca9(Mgiron, Fe)(PO4)6PO3Ohydrogen, H. It is a relatively rare mineral but is found in granitic pegmatites, phosphate rock deposits, guano caves a ...

References

;Bibliography * * *

External links

{{commonscat-inline, Messelite, lcfirst=yes Triclinic minerals Calcium minerals Iron(II) minerals Manganese(II) minerals Phosphate minerals Hydrates Minerals in space group 2