Clinohedrite

Clinohedrite is a rare silicate mineral. Its chemical composition is a hydrous calcium-zinc silicate; CaZn(SiO₄)·H₂O. It crystallizes in the monoclinic system and typically occurs as veinlets and fracture coatings. It is commonly colorless, white to pale amethyst in color. It has perfect cleavage and the crystalline habit has a brilliant luster. It has a Mohs hardness of 5.5 and a specific gravity of 3.28 - 3.33.[2][3]

Clinohedrite
Clinohedrite coating hardystonite, franklinite with willemite reaction rims. Franklin, New Jersey. Orange fluorescence under UV.
General
Category	Silicate mineral
Formula (repeating unit)	CaZn(SiO4)·H2O
Strunz classification	9.AE.30
Dana classification	52.2.1.2
Crystal system	Monoclinic
Crystal class	Domatic (m) (same H-M symbol)
Space group	Cc
Unit cell	a = 5.09 Å, b = 15.82 Å, c = 5.38 Å; β = 103.39°; Z = 4
Identification
Color	Colorless to brown surface coating, clear to pale pink to amethystine crystals
Crystal habit	Thin to thick or platey surface and fracture coatings, in vugs or cavities, rarely as crusts of crystals - prismatic to tabular, may be wedge-shaped
Cleavage	Perfect on {010}
Mohs scale hardness	5.5
Luster	Brilliant, glassy; pearly on {010}
Streak	white
Diaphaneity	Transparent to translucent
Specific gravity	3.28 - 3.33
Optical properties	Biaxial (-)
Refractive index	nα = 1.662 nβ = 1.667 nγ = 1.669
Ultraviolet fluorescence	UV=orange
Other characteristics	Strongly pyroelectric
References	[1][2][3][4]

Under short wave ultraviolet light it fluoresces a rich orange color. It is frequently associated with minerals such as hardystonite (fluoresces violet blue), esperite (fluoresces bright yellow), calcite (fluoresces orange-red), franklinite (non-fluorescent) and willemite (fluoresces green).[5]

Clinohedrite was found primarily at the Franklin zinc mines in New Jersey, the type locality, but has also been reported from the Christmas mine, Gila County, Arizona,[2] and the Western Quinling gold belt, Gansu Province, China.[3]

It was first described in 1898 and was named for its crystal morphology from the Greek klino for incline, and hedra for face.[2]