Formula: Ca12Al14O32[☐(sub>4Cl2]
Multiple oxide
Specific gravity: 2.85 calculated
Streak: White
Colour: Colourless

Metamorphic environments

The mayenite supergroup species show unique electrochemichal properties, with some anions in their structure (such as oxygen anions) migrating thorough the structure. As such, the mayenites behave as metals even though they are very non-metal in terms of general chemistry. Transitions seen in their structure may be related to superconducting. The mayenites represent a group of chemicals known as "salts of an electron", also known as electrides (Mindat).


At the Basalt quarry, Klöch, Südoststeiermark District, Styria, Austria, chlormayenite is associated with melilite, wollastonite, kalsilite, brownmillerite and corundum (HOM).

There are two co-type localities, Mayener Feld, Mayen, and Ettringer Feld, Ettringen, both at Vordereifel, Mayen-Koblenz District, Rhineland-Palatinate, Germany. Here chlormayenite occurs in thermally metamorphosed limestone blocks included in volcanic rocks. The chlormayenite is found as colourless rounded grains having no recognisable crystal faces, with a maximum diameter of 60 microns. Associated minerals include calcite, ettringite, wollastonite, larnite, brownmillerite, gehlenite, diopside, pyrrhotite, grossular, spinel, afwillite, jennite, portlandite and jasmundite (AM 50.2106-2107).

At the Hatrurim Basin, Tamar Regional Council, Southern District, Israel, chlormayenite is common in high-temperature, thermally metamorphosed, impure limestone. Associated minerals include spurrite, larnite, grossite and brownmillerite (HOM).

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