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Brownmillerite is a rare oxide mineral 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 census. Easton is located at the confluence of the Lehigh River, a river that joins the Delaware R ...
.


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 is the second most populous country in Europe after Russia, and the most populous member state of the European Union. Germany is situated betwe ...
. At the type locality the mineral occurs within limestone blocks that are contained in a
volcanic A volcano is a rupture 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 found where tectonic plates a ...
flow. The limestone blocks had undergone thermal metamorphism. The mineral also occurs in the thermally altered strata of the
Hatrurim Formation The Hatrurim Formation or ''Mottled Zone'' is a geologic formation with outcrops all around the Dead Sea Basin: in the Negev Desert in Israel, in the Judaean Desert on the West Bank, and in western Jordan. It includes late Cretaceous to Eocene age ...
of
Israel Israel (; he, יִשְׂרָאֵל, ; ar, إِسْرَائِيل, ), officially the State of Israel ( he, מְדִינַת יִשְׂרָאֵל, label=none, translit=Medīnat Yīsrāʾēl; ), is a country in Western Asia. It is situated ...
. Minerals associated with brownmillerite in the Mayen locality include calcite, ettringite,
wollastonite Wollastonite is a calcium inosilicate mineral ( Ca Si O3) that may contain small amounts of iron, magnesium, and manganese substituting for calcium. It is usually white. It forms when impure limestone or dolomite is subjected to high temperature ...
,
larnite Larnite is a calcium silicate mineral with formula: Ca2SiO4. It is the calcium member of the olivine group of minerals. It was first described from an occurrence at Scawt Hill, Larne, Northern Ireland in 1929 by Cecil Edgar Tilley and named ...
,
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 pyrometamorphic sites such a ...
,
gehlenite Gehlenite, (Ca2Al lSiO7, is a sorosilicate, Al-rich endmember of the melilite complete solid solution series with akermanite.Deer et al., 1993 The type locality is in the Monzoni Mountains, Fassa Valley in Trentino in Italy, and is named after ...
,
diopside Diopside is a monoclinic pyroxene mineral with composition . It forms complete solid solution series with hedenbergite () and augite, and partial solid solutions with orthopyroxene and pigeonite. It forms variably colored, but typically dull ...
,
pyrrhotite Pyrrhotite is an iron sulfide mineral with the formula Fe(1-x)S (x = 0 to 0.2). It is a nonstoichiometric variant of FeS, the mineral known as troilite. Pyrrhotite is also called magnetic pyrite, because the color is similar to pyrite and it i ...
,
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 t ...
, spinel,
afwillite Afwillite is a calcium hydroxide nesosilicate mineral with formula Ca3(SiO3OH)2·2H2O. It occurs as glassy, colorless to white prismatic monoclinic crystals. Its Mohs scale hardness is between 3 and 4. It occurs as an alteration mineral in cont ...
,
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
Austria Austria, , bar, Östareich officially the Republic of Austria, is a country in the southern part of Central Europe, lying in the Eastern Alps. It is a federation of nine states, one of which is the capital, Vienna, the most populous ...
n occurrence near Kloch,
melilite Melilite refers to a mineral of the melilite group. Minerals of the group are solid solutions of several endmembers, the most important of which are gehlenite and åkermanite. A generalized formula for common melilite is ( Ca, Na)2( Al, Mg, ...
, mayenite, wollastonite,
kalsilite Kalsilite ( K Al Si O4) is a vitreous white to grey feldspathoidal mineral that is found in some potassium-rich lavas, such as from Chamengo Crater in Uganda. It has a relative hardness In materials science, hardness (antonym: softness) is a ...
and corundum 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. (19 ...
, 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, stucco, and non-specialty grout. It was developed from other types of hydraulic lime in England in the early 19th ...
.


Use as a catalyst

Brownmillerite has been found to be a highly active oxygen evolution reaction catalyst in neutral pH.


See also

*
Ye'elimite Ye'elimite is the naturally occurring form of anhydrous calcium sulfoaluminate, . It gets its name from Har Ye'elim in Israel in the Hatrurim Basin west of the Dead Sea where it was first found in nature by Shulamit Gross, an Israeli mineralogi ...
, , a rare natural anhydrous calcium sulfoaluminate


References

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