:White eylettersite (in the cavity), with brown to amber mundite and greenish threadgoldite; bought from prof. van Wambeke who discovered the mineral and named it after his wife, Lea Eyletters. Collection and photo Erik Vercammen. Locality: Kobokobo pegmatite, Mwenga, Sud-Kivu, Democratic Republic of the Congo SIze: 11mm x 5mm x 6mm — Photo: Erik Vercammen · CC BY 3.0
Eylettersite
Eylettersite is an IMA-recognized mineral species in the phosphate class, with the chemical formula Th₀.₇₅Al₃(PO₄)₂(OH)₆.
It crystallizes in the hexagonal crystal system (space group R-3m). It is a member of the Alunite-crandallite structural group.
Key properties: specific gravity 3.38–3.44; optically uniaxial.
IMA symbol Eyl, IMA status: approved, named in 1969.
An alteration product of thorian crandallite in a phosphate-rich granite pegmatite.
It is found associated with Autunite, phosphuranylite, fluorapatite, “limonite”, feldspar, “cyrtolite”.
The name refers to the wife of the discoverer, Mme. Van Wambeke.