Dollaseite-(Ce)

Dollaseite-(Ce)
General
Category	Silicate mineral
Formula (repeating unit)	CaCeMg2AlSi3O11F(OH)
IMA symbol	Dls-Ce[1]
Crystal system	Monoclinic
Crystal class	Prismatic (2/m) (same H-M symbol)
Space group	P21/m
Identification
Formula mass	551.04 g/mol
Color	Brown
Crystal habit	Massive, somewhat prismatic, equant when subhedral
Twinning	On [100]
Cleavage	Indistinct, epidote has one good cleavage on one side
Fracture	Flat regular to uneven
Mohs scale hardness	6.5–7
Luster	Vitreous
Streak	light brown
Diaphaneity	Translucent
Specific gravity	3.9
Optical properties	Biaxial (+)
Refractive index	nα = 1.715 nβ = 1.718 nγ = 1.733
Birefringence	δ = 0.018
Pleochroism	Strong
References	[2][3][4][5]

Dollaseite-(Ce) is a sorosilicate end-member epidote rare-earth mineral which was discovered by Per Geijer (1927) in the Ostanmossa mine (Östanmossa gruva), Norberg district, Sweden. Dollaseite-(Ce), although not very well known, is part of a broad epidote group of minerals which are primarily silicates, the most abundant type of minerals on earth. Dollaseite-(Ce) forms as dark-brown subhedral crystals primarily in Swedish mines. With the ideal chemical formula, CaREE³⁺
Mg
₂AlSi
₃O
₁₁,(OH)F, dollaseite-(Ce) can be partially identified by its content of the rare earth element cerium.