Brownmillerite

Brownmillerite is a rare oxide mineral with chemical formula Ca2(Al,Fe)2O5. It is named for Lorrin Thomas Brownmiller (1902–1990), chief chemist of the Alpha Portland Cement Company, Easton, Pennsylvania.

Brownmillerite
Red/red-brown crystals of brownmillerite from Caspar quarry, Bellerberg Volcano, Ettringen, Mayen, Eifel Mts, Rhineland-Palatinate, Germany
General
CategoryOxide mineral
Formula
(repeating unit)		Ca2(Al,Fe)2O5
Strunz classification4.AC.10
Dana classification7.11.2.1
Crystal systemOrthorhombic
Crystal classDipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)
Space groupIbm2
Unit cella = 5.57 Å, b = 14.52 Å,
c = 5.34 Å; Z = 4
Identification
ColorReddish brown
Crystal habitAs minute square platelets; massive
DiaphaneitySemitransparent
Specific gravity3.76
Optical propertiesBiaxial (-)
Refractive indexnα = 1.960 nβ = 2.010 nγ = 2.040
Birefringenceδ = 0.080
PleochroismDistinct; X = Y = yellow-brown; Z = dark brown
2V angle75° (measured)
References[1][2][3][4]

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.[3]

At the type locality the mineral occurs within limestone blocks that are contained in a volcanic flow. The limestone blocks had undergone thermal metamorphism. The mineral also occurs in the thermally altered strata of the Hatrurim Formation of Israel. Minerals associated with brownmillerite in the Mayen locality include calcite, ettringite, wollastonite, larnite, mayenite, gehlenite, diopside, pyrrhotite, grossular, spinel, afwillite, jennite, portlandite and jasmundite. In an Austrian occurrence near Kloch, melilite, mayenite, wollastonite, kalsilite and corundum are found. Within the Hatrurim area spurrite, larnite and mayenite are associated.[2]

The mineral is similar to the calcium aluminoferrite phases which are commonly found as components of Portland cement.

Use as a catalyst

Brownmillerite has been found to be a highly active oxygen evolution reaction catalyst in neutral pH.[5]


gollark: I assumed it was, was it not?
gollark: It *should* probably not crash the compiler horribly, to be fair.
gollark: I'm very jealous. *I* never had an ICE.
gollark: Fun!
gollark: Worrying.

References
  1. Mineralienatlas
  2. Handbook of Mineralogy - Brownmillerite
  3. Mindat.org - Brownmillerite
  4. Brownmillerite data on Webmineral.com
  5. Zhou, Li Qin; Ling, Chen; Zhou, Hui; Wang, Xiang; Liao, Joseph; Reddy, Gunugunuri K.; Deng, Liangzi; Peck, Torin C. (2019-09-09). "A high-performance oxygen evolution catalyst in neutral-pH for sunlight-driven CO2 reduction". Nature Communications. 10 (1): 4081. Bibcode:2019NatCo..10.4081Z. doi:10.1038/s41467-019-12009-8. PMC 6733866. PMID 31501446.
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.