Brownmillerite is a rare

oxide mineral The oxide mineral class includes those minerals in which the oxide anion (O2−) is bonded to one or more metal alloys. The hydroxide-bearing minerals are typically included in the oxide class. Minerals with complex anion groups such as the sil ...

with chemical formula . It is named for Lorrin Thomas Brownmiller (1902–1990), chief chemist of the Alpha Portland Cement Company,

Easton, Pennsylvania Easton is a city in and the county seat of Northampton County, Pennsylvania, United States. The city's population was 28,127 as of the 2020 United States census, 2020 census. Easton is located at the confluence of the Lehigh River and the Delawa ...

Discovery and occurrence

The chemical compound was first recognized in 1932 and named for the chemist who identified it. The naturally occurring mineral form of the compound was first recognized in 1964 for occurrences in the Bellerberg volcano, Ettringen, Mayen-Koblenz,

Germany Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...

. At the type locality the mineral occurs within

limestone block Limestone is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Limestone forms when these ...

s that are contained in a

volcanic A volcano is commonly defined as a vent or fissure in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often fo ...

flow. The limestone blocks had undergone thermal metamorphism. The mineral also occurs in the thermally altered

strata In geology and related fields, a stratum (: strata) is a layer of Rock (geology), rock or sediment characterized by certain Lithology, lithologic properties or attributes that distinguish it from adjacent layers from which it is separated by v ...

of the Hatrurim Formation of

Israel Israel, officially the State of Israel, is a country in West Asia. It Borders of Israel, shares borders with Lebanon to the north, Syria to the north-east, Jordan to the east, Egypt to the south-west, and the Mediterranean Sea to the west. Isr ...

. Minerals associated with brownmillerite in the Mayen locality include

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 ...

, ettringite,

wollastonite Wollastonite is a calcium Silicate minerals, inosilicate mineral (calcium, Casilicon, Sioxygen, O3) that may contain small amounts of iron, magnesium, and manganese substituting for calcium. It is usually white. It forms when impure limestone or D ...

, larnite,

mayenite Chlormayenite (after Mayen, Germany), Ca12Al14O32 ��4Cl2 is a rare calcium aluminium oxide mineral of cubic symmetry. It was originally reported from Eifel volcanic complex (Germany) in 1964. It is also found at Pyrometamorphism, pyrometamorp ...

, gehlenite, diopside,

pyrrhotite Pyrrhotite (''Pyrrhus of Epirus, pyrrhos'' in Greek language, Greek meaning "flame-coloured"'')'' is an iron sulfide mineral with the formula Fe(1−x)S (x = 0 to 0.125). It is a nonstoichiometric compound, nonstoichiometric variant of FeS, th ...

grossular Grossular is a calcium-aluminium species of the garnet group of minerals. It has the chemical formula of Ca3Al2(SiO4)3 but the calcium may, in part, be replaced by ferrous iron and the aluminium by ferric iron. The name grossular is derived from ...

spinel Spinel () is the magnesium/aluminium member of the larger spinel group of minerals. It has the formula in the cubic crystal system. Its name comes from the Latin word , a diminutive form of ''spine,'' in reference to its pointed crystals. Prop ...

, afwillite,

jennite Jennite is a calcium silicate hydrate mineral of general chemical formula: Ca9Si6O18(OH)6·8H2O. Jennite occurs as an alteration mineral in metamorphosed limestone and skarn. It typically occurs as vein and open space fillings as a late minera ...

, portlandite and jasmundite. In an

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n occurrence near Kloch, melilite, mayenite, wollastonite, kalsilite and

corundum Corundum is a crystalline form of aluminium oxide () typically containing traces of iron, titanium, vanadium, and chromium. It is a rock (geology), rock-forming mineral. It is a naturally transparency and translucency, transparent material, but ...

are found. Within the Hatrurim area

spurrite Spurrite is a white, yellow or light blue mineral with monoclinic crystals. Its chemical formula is Ca5( Si O4)2 CO3. Spurrite is generally formed in contact metamorphism zones as mafic magmas are intruded into carbonate rocks.Smith, J.V. (196 ...

, larnite and mayenite are associated. The mineral is similar to the calcium aluminoferrite phases which are commonly found as components of

Portland cement Portland cement is the most common type of cement in general use around the world as a basic ingredient of concrete, mortar (masonry), mortar, stucco, and non-specialty grout. It was developed from other types of hydraulic lime in England in th ...

Use as a catalyst

Brownmillerite has been found to be a highly active

oxygen evolution Oxygen evolution is the chemical process of generating diatomic oxygen (O2) by a chemical reaction, usually from water, the most abundant oxide compound in the universe. Oxygen evolution on Earth is effected by biotic oxygenic photosynthesis, pho ...

reaction catalyst in neutral pH.

References

{{reflist Oxide minerals Orthorhombic minerals Minerals in space group 46

Discovery and occurrence

Use as a catalyst

See also

References