Fluoborite has a chemical formula of Mg₃(BO₃)(F,OH)₃. Its name comes from its main chemical components,

fluorine Fluorine is a chemical element; it has Chemical symbol, symbol F and atomic number 9. It is the lightest halogen and exists at Standard temperature and pressure, standard conditions as pale yellow Diatomic molecule, diatomic gas. Fluorine is extre ...

and

boron Boron is a chemical element; it has symbol B and atomic number 5. In its crystalline form it is a brittle, dark, lustrous metalloid; in its amorphous form it is a brown powder. As the lightest element of the boron group it has three ...

. It was first described in 1926. Fluoborite's crystal system is hexagonal, meaning it has one six-fold axis of rotation. It also has a mirror plane perpendicular to the c-axis. Fluoborite is uniaxial, just like all other hexagonal minerals. Uniaxial means it has only one optic axis. It is anisotropic. Its relief is low, and it is birefringent. There are three major settings fluoborite is found. It is found in

skarn Skarns or tactites are coarse-grained metamorphic rocks that form by replacement of carbonate-bearing rocks during regional or contact metamorphism and metasomatism. Skarns may form by metamorphic recrystallization of impure carbonate protoliths, ...

s developed in metamorphosed boron-rich magnesium rocks, contact metamorphosed

marble Marble is a metamorphic rock consisting of carbonate minerals (most commonly calcite (CaCO3) or Dolomite (mineral), dolomite (CaMg(CO3)2) that have recrystallized under the influence of heat and pressure. It has a crystalline texture, and is ty ...

, and in contact

metasomatic 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 traditionally defined as metamorphism which involves a change in the chemical com ...

magnetite Magnetite is a mineral and one of the main iron ores, with the chemical formula . It is one of the iron oxide, oxides of iron, and is ferrimagnetism, ferrimagnetic; it is attracted to a magnet and can be magnetization, magnetized to become a ...

deposits. There are two major type localities for fluoborite. One is Tall Mine, Kallmora,

Norberg Norberg () is a locality and the seat of Norberg Municipality in Västmanland County, Sweden with 4,518 inhabitants in 2010. Best known for the Norbergfestival which is Scandinavias biggest electronic music festival, organized in an old iron or ...

Västmanland Västmanland ( or ) is a historical Swedish province, or , in middle Sweden. It borders Södermanland, Närke, Värmland, Dalarna and Uppland. Västmanland means "West Man Land" or, less literally, "The Land of the Western Men", where the "we ...

Sweden Sweden, formally the Kingdom of Sweden, is a Nordic countries, Nordic country located on the Scandinavian Peninsula in Northern Europe. It borders Norway to the west and north, and Finland to the east. At , Sweden is the largest Nordic count ...

. It is an iron mine in a contact metasomatic magnetite deposit. The other type locality is the Huerta del Vinagre mine,

Spain Spain, or the Kingdom of Spain, is a country in Southern Europe, Southern and Western Europe with territories in North Africa. Featuring the Punta de Tarifa, southernmost point of continental Europe, it is the largest country in Southern Eur ...

. It occurs associated with

ludwigite Ludwigite is a magnesium-iron borate mineral: Mg2FeBO5. Ludwigite typically occurs in magnesian iron skarn and other high temperature contact metamorphic deposits. It occurs in association with magnetite, forsterite, clinohumite and the borates ...

chondrodite Chondrodite is a nesosilicate mineral with formula . Although it is a fairly rare mineral, it is the most frequently encountered member of the humite group of minerals. It is formed in hydrothermal deposits from locally metamorphosed dolomite ...

and

calcite Calcite is a Carbonate minerals, carbonate mineral and the most stable Polymorphism (materials science), polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on ...

in the Tallgruvan, Sweden occurrence. It occurs with mooreite,

willemite Willemite is a zinc silicate mineral () and a minor ore of zinc. It is highly fluorescent (green) under shortwave ultraviolet light. It occurs in a variety of colors in daylight, in fibrous masses and apple-green gemmy masses. Troostite is a vari ...

fluorite Fluorite (also called fluorspar) is the mineral form of calcium fluoride, CaF2. It belongs to the halide minerals. It crystallizes in isometric cubic habit, although octahedral and more complex isometric forms are not uncommon. The Mohs scal ...

hydrozincite Hydrozincite, also known as zinc bloom or marionite, is a white carbonate mineral consisting of Zn5( CO3)2( OH)6. It is usually found in massive rather than crystalline form. It occurs as an oxidation product of zinc ores and as post mine inc ...

, pyrochroite,

zincite Zincite is the mineral form of zinc oxide ( Zn O). Its crystal form is rare in nature; a notable exception to this is at the Franklin and Sterling Hill Mines in New Jersey, an area also famed for its many fluorescent minerals. It has a hexago ...

and

rhodochrosite Rhodochrosite is a manganese carbonate mineral with chemical composition Manganese(II) carbonate, MnCO3. In its pure form (rare), it is typically a rose-red colour, but it can also be shades of pink to pale brown. It Streak (mineralogy), streak ...

Sterling Hill The Sterling Hill Mine, now known as the Sterling Hill Mining Museum, is a former zinc mine in Ogdensburg, Sussex County, New Jersey, United States. It was the last working underground mine in New Jersey. It closed in 1986, and became a mus ...

New Jersey New Jersey is a U.S. state, state located in both the Mid-Atlantic States, Mid-Atlantic and Northeastern United States, Northeastern regions of the United States. Located at the geographic hub of the urban area, heavily urbanized Northeas ...

References

{{Reflist Borate minerals Magnesium minerals Hexagonal minerals Minerals in space group 176