Fluorellestadite , Hemimorphite Locality: Mapimí , Municipio de Mapimí , Durango , Mexico ( Locality at mindat.org ) Size: thumbnail, 2.7 x 2.7 x 1.7 cm Fluorellestadite ps. Hemimorphite (wilkeite) A truly amazing pseudomorph with SHARP blades up to .7 cm. Although small overall, this is the best example I have yet seen of this classic replacement which used to be called by the name of wilkeite. The pics say it all. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Fluorellestadite
A rare apatite-group calcium nesosilicate carrying sulfate and fluorine, in series with hydroxylellestadite.
Intro adapted from Wikipedia (CC BY-SA).
Fluorellestadite is an IMA-recognized mineral species in the silicate class, with the chemical formula Ca₅(SiO₄)₁.₅(SO₄)₁.₅F.
It crystallizes in the hexagonal crystal system (space group P6_3/m). It is a member of the Apatite structural group.
Key properties: Mohs hardness 4.5; specific gravity 3.03; White with weak bluish tint streak; Vitreous to greasy luster; refractive index 1.77; optically uniaxial.
IMA symbol Fel, IMA status: approved, named in 1987.
Formed in burned fragments of petrified wood in coal dumps (Kopeysk, Russia).
It is found associated with Lime, periclase, magnesioferrite, hematite, srebrodolskite, anhydrite.
The name refers to fluorine in the chemical composition and analogy to ellestadite.