Weilite

Weilite (CaHAsO₄) is a rare arsenate mineral. It is a translucent white triclinic mineral with a waxy luster.^[2]

Weilite
Weilite (white) with pink erythrite from Richelsdorf District, Wildeck, Hesse, Germany
General
Category	Arsenate mineral
Formula	CaHAsO4
IMA symbol	Wei[1]
Strunz classification	8.AD.10
Crystal system	Triclinic
Crystal class	Pinacoidal (1) (same H-M symbol)
Space group	P1
Unit cell	a = 7.059 Å, b = 6.891 Å c = 7.201 Å; α = 97.43° β = 103.55°, γ = 87.75°; Z = 4
Identification
Color	White
Crystal habit	Powdery, massive
Fracture	Irregular/uneven
Tenacity	Brittle
Luster	Waxy, greasy, dull
Streak	White
Diaphaneity	Translucent
Specific gravity	3.48
Optical properties	Biaxial (-)
Refractive index	nα = 1.644 nγ = 1.688
Birefringence	δ = 0.044
2V angle	Measured: 81°
References	[2][3][4]

It was first described in 1963 for occurrences in Gabe Gottes Mine, Haut-Rhin, Alsace, France; Wittichen, Schenkenzell, Black Forest, Baden-Württemberg, Germany; and the Schneeberg District, Erzgebirge, Saxony, Germany. It is named after French mineralogist René Weil of the University of Strasbourg.^[2] It occurs in the oxidized zone of arsenic-bearing hydrothermal veins. It occurs as an alteration product of pharmacolite and haidingerite.^[3][4]