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Category Oxide mineral
(repeating unit)
Strunz classification 04.CC.20
Crystal symmetry Isometric hextetrahedral
H-M symbol: (43m)
Space group: I43d
Unit cell a = 11.98 Å; Z=2
Color Colorless
Crystal habit Microscopic anhedral grains
Crystal system Cubic
Streak White
Diaphaneity Transparent
Specific gravity 2.85
Optical properties Isotropic
Refractive index n = 1.614–1.643
Alters to Absorbs water on exposure
References [1][2][3]

Mayenite (after Mayen, Germany), Ca12Al14O33, 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 as in the Hatrurim Formation of Israel and in some burned coal dumps.[4][1][2]

It occurs in thermally altered limestone xenoliths within basalts in Mayen, Germany and Klöch, Styria, Austria. In the Hatrurim of Israel it occurs in thermally altered limestones. It occurs with calcite, ettringite, wollastonite, larnite, brownmillerite, gehlenite, diopside, pyrrhotite, grossular, spinel, afwillite, jennite, portlandite, jasmundite, melilite, kalsilite and corundum in the limestone xenoliths. In the Hatrurim it occurs with spurrite, larnite, grossite and brownmillerite.[1]

The formula can be written as [Ca12Al14O32]O,[5] which refers to the unique feature: anion diffusion process.[6]

Mayenite is also found as calcium aluminate in cement where its formula is also written as 12 CaO · 7 Al2O3, or C12A7 in the cement chemist notation.

See also[edit]


  1. ^ a b c Handbook of Mineralogy
  2. ^ a b Mindat
  3. ^ Mayenite data on Webmineral
  4. ^ Sokol E.V., Maksimova N.V., Nigmatulina E.N., Sharygin V.V. and Kalugin V.M. (2005) Combustion metamorphism, Novosibirsk: Publishing House of the SB RAS.
  5. ^ Palacios L., Cabeza A., Bruque S., García-Granda S. and Aranda M.A.G. (2008) Structure and Electrons in Mayenite Electrides. Inorganic Chemistry, 47(7), pp. 2661–2667.
  6. ^ Boysen H., Kaiser-Bischoff I. and Lerch M. (2007) Anion Diffusion Processes in O- and N-Mayenite Investigated by Neutron Powder Diffraction. Bunsen Colloquium: Diffusion and Reactions in Advanced Materials (September 27th–28th, Clausthal-Zellerfeld, Germany) / The Open-Access Journal for the Basic Principles of Diffusion Theory, Experiment and Application.