Devilline

Devilline is a sulfate mineral with the chemical formula CaCu₄(SO₄)₂(OH)₆·3H₂O. The name originates from the French chemist's name, Henri Etienne Sainte-Claire Deville (1818–1881).

Devilline
Devilline
General
Category	Sulfate minerals
Formula	CaCu4(SO4)2(OH)6·3(H2O)
IMA symbol	Dev[1]
Strunz classification	7.DD.30
Crystal system	Monoclinic
Crystal class	Prismatic (2/m) (same H-M symbol)
Space group	P21/c
Unit cell	a = 20.870, b = 6.135 c = 22.91 [Å], β = 102.73° V = 2,861.23 Å3
Identification
Color	Green, blueish green; green in transmitted light
Crystal habit	Prismatic, lamellar, platy pseudohexagonal crystals
Twinning	On {010}
Cleavage	Perfect (001) distinct (110) and (101)
Tenacity	Brittle
Mohs scale hardness	2.5
Luster	Vitreous, pearly
Streak	Light green
Density	Measured: 3.13 g/cm3 Calculated: 3.084 g/cm3
Optical properties	biaxial negative
Refractive index	nα=1.585, nβ=1.649, nγ=1.660
Birefringence	δ=0.075
Pleochroism	Visible
2V angle	42°
Solubility	Insoluble in water and concentrated H2SO4. Completely soluble in HNO3.
References	[2][3]

Devilline crystallizes in the monoclinic system.^[4] Crystallographically, it contains three vectors of unequal lengths and two pairs of vectors are perpendicular while the other pair makes an angle other than 90°. Devilline is prismatic and belongs to the crystal class 2/m. This mineral belongs to the space group P 2₁/c. Devilline is an anisotropic mineral, meaning that the mineral has different properties in different directions. Optically, this mineral is biaxial negative, meaning that it contains two optic axes. Devilline has a moderate mineral relief. Mineral relief refers to the way a mineral appears to stand out when viewed under polarized light and it is dependent on the mineral's index of refraction.

Devilline is a rare and unusual secondary mineral found in the oxidized portions of copper sulfide ore deposits.^[5] Because Devilline occurs in such oxidation zones, this mineral often is of post-mining origin. Devilline is found in mines all around the world.

Devilline group

Devilline group minerals are monoclinic sulfates.^[6]

Mineral	Chemical formulae	Crystal system
Campigliaite	Cu4Mn2+(SO4)2(OH)6·4H2O	Monoclinic
Devilline	CaCu4(SO4)2(OH)6·3H2O	Monoclinic
Kobyashevite	Cu5(SO4)2(OH)6·4H2O	Triclinic
Ktenasite	Zn(Cu,Zn)4(SO4)2(OH)6·6H2O	Monoclinic
Lautenthalite	PbCu4(SO4)2(OH)6·3H2O	Monoclinic
Serpierite	Ca(Cu,Zn)4(SO4)2(OH)6·3H2O	Monoclinic