Chloroxiphite

Chloroxiphite is a rare olive green to pistacio green lead copper halide mineral with formula: Pb₃CuO₂Cl₂(OH)₂.

Chloroxiphite
Chloroxiphite crystal (dark green) embedded in mendipite. The bright blue material is diaboleite.
General
Category	Halide mineral
Formula (repeating unit)	Pb3CuO2Cl2(OH)2
IMA symbol	Cxp[1]
Strunz classification	3.DB.30
Crystal system	Monoclinic
Crystal class	Prismatic (2/m) (same H-M symbol)
Space group	P21/m
Unit cell	a = 6.6972(8) Å, b = 5.7538(5) Å, c = 10.4686(14) Å; β = 97.747(10)°; Z = 2
Identification
Color	Dull olive green to pistachio-green
Crystal habit	Elongated, flatenned, striated and often curved crystals and groups
Cleavage	Perfect on {101}, distinct on {100}
Tenacity	Very brittle, friable
Mohs scale hardness	2+1⁄2
Luster	Adamantine, resinous
Streak	Light green yellow
Diaphaneity	Transparent
Specific gravity	6.76 - 6.93
Optical properties	Biaxial (-)
Refractive index	nα = 2.160 nβ = 2.240 nγ = 2.250
Birefringence	δ = 0.090
Pleochroism	Visible: Y = yellowish brown; Z = bright emerald-green
2V angle	Measured: ~70°
References	[2][3][4][5]

It was first discovered in 1923 in the Mendip Hills, Somerset, England associated with mendipite.[3] Like mendipite it is an oxychloride mineral and formed from the alteration of lead ore (galena) by secondary oxidation. In addition to mendipite, it occurs with diaboleite, parkinsonite, wulfenite, cerussite and hydrocerussite.[5] Its name comes from the Greek words (χλωρός) "green", describing its color, and (ζιφος) "blade" as its crystal form is long blade-like crystals that often show the growth pattern and time taken to form.[3]