Fontarnauite

Fontarnauite is a relatively recently described, rare sulfate, borate mineral with the chemical formula (Na,K)₂(Sr,Ca)(SO₄)[B₅O₈(OH)]·2H₂O. It is found in an evaporite boron deposit. It coexists with other evaporite boron minerals, especially probertite. It is monoclinic, crystallizing in the space group P2₁/c.^[4][2]

CategoryBorate minerals

Formula(Na,K)₂(Sr,Ca)(SO₄)[B₅O₈(OH)]·2H₂O

IMA symbolFon^[1]

Strunz classification6.DA.60

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Fontarnauite
Fontarnauite, Anatolia, West Turkey
General
Category	Borate minerals
Formula	(Na,K)2(Sr,Ca)(SO4)[B5O8(OH)]·2H2O
IMA symbol	Fon[1]
Strunz classification	6.DA.60
Crystal system	Monoclinic
Crystal class	Prismatic (2/m) (same H-M symbol)
Space group	P21/c
Identification
Color	Light brown
Cleavage	Perfect {010}
Mohs scale hardness	2.5 - 3
References	[2][3]

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It was named for Ramon Fontarnau i Griera, a materials scientist of the University of Barcelona.^[2]