Åkermanite Field of view: 2 mm Locality: Graulay quarry, Hillesheim, Gerolstein, Vulkaneifel, Rhineland-Palatinate, Germany ( locality at mindat.org ) — Photo: Henk Smeets – tomeikminerals.com · CC BY 4.0
Åkermanite
A calcium-magnesium member of the melilite group that forms when silica-rich limestone or dolomite is baked by contact metamorphism.
Intro adapted from Wikipedia (CC BY-SA).
Åkermanite is an IMA-recognized mineral species in the silicate class, with the chemical formula Ca₂MgSi₂O₇.
It crystallizes in the tetragonal crystal system (space group P-42_1m). It is a member of the Melilite structural group.
Key properties: Mohs hardness 5–6; specific gravity 2.944; Vitreous to resinous luster; refractive index 1.636; optically uniaxial.
IMA symbol Åk, grandfathered status — known before the IMA’s founding, named in 1884.
A product of contact metamorphism of siliceous limestones and dolostones, and in rocks of the sanidinite facies. Also forms from alkalic magmas rich in calcium.
It is found associated with Monticellite, wollastonite, spurrite, larnite, merwinite, \fassaite, " grossular, diopside, forsterite.
The name refers to Anders Richard º Akerman (1837–1922), Swedish metallurgist.