Leverettite from the Torrecillas mine, Iquique Provence, Chile: the Co-analogue of herbertsmithite

Abstract

The new mineral leverettite (IMA 2013-011), ideally Cu3CoCl2(OH)6, was found at the Torrecillas mine, Salar Grande, Iquique Province, Chile, where it occurs as a supergene alteration phase in association with akaganéite, anhydrite, chalcophanite, goethite, halite, manganite, pyrite, quartz and todorokite. Crystals of leverettite are steep rhombohedra to 1 mm with {101} prominent and modified by {001}, sometimes forming V-shaped twins by reflection on {10}. The crystals can also form finger-like, parallel stacked growths along the c axis. The new mineral is medium to deep green in colour and has a light green streak. Crystals are transparent with a vitreous lustre. Mohs hardness is ∼3 and the crystals have a brittle tenacity, a perfect cleavage on {101} and a conchoidal fracture. The measured density is 3.64(2) g cm–3 and calculated density based on the empirical formula is 3.709 g cm–3. Optically, leverettite is uniaxial (–) with ω and ε > 1.8 and exhibits pleochroism with O (bluish green) > E (slightly yellowish green). The empirical formula, determined from electron-microprobe analyses is Cu3(Co0.43Cu0.40Mn0.17Ni0.07Mg0.01)Σ1.08Cl1.87O6.13H6. Leverettite is trigonal (hexagonal), space group Rm, unit-cell parameters a = 6.8436(6) and c = 14.064(1) Å, V = 570.42(8) Å3, Z = 3. The eight strongest X-ray powder diffraction lines are [dobs Å (I)(hkl)]: 5.469(90)(101), 4.701(18)(003), 2.905(22)(021), 2.766(100)(113), 2.269(66)(024), 1.822(26)(033), 1.711(33)(220), 1.383(23)(128). The structure, refined to R1 = 0.023 for 183 Fo > 4σF reflections, shows leverettite to be isostructural with herbertsmithite and gillardite.

Structural complexity and crystallization: the Ostwald sequence of phases in the Cu2(OH)3Cl system (botallackite–atacamite–clinoatacamite)

“…4. The condensation of chains by sharing common Cu corners leaves one of the Cu atoms not bonded to Cl, and this is the position that is substituted by Zn, Mg and Ni in other atacamite group minerals [44][45][46][47][48][49].…”

Quantum magnetism in minerals

“…Apart from the most studied herbertsmithite, structurally perfect S = 1/2 KAFM lattices are also realized in its isostructural Mg, Ni, and Co analogues tondiite, γ-MgCu 3 (OH) 6 Cl 2 [372,373], gillardite, γ-NiCu 3 (OH) 6 Cl 2 [374], and leverettite, γ-CoCu 3 (OH) 6 Cl 2 [375]. The lattice parameters of tondiite and leverettite are very close to those of herbertsmithite, whereas gillardite has a smaller c lattice constant due to the smaller radius of the Ni 2+ ion as…”

Structural and spectroscopic study of well-developed crystals of parahibbingite, β-Fe2(OH)3Cl, formed from terrestrial weathering of the Muonionalusta iron meteorite

“…Parahibbingite is isostructural with herbertsmithite, Cu 3 Zn(OH) 6 Cl 2 (Braithwaite et al , 2004), gillardite, Cu 3 Ni(OH) 6 Cl 2 (Clissold et al , 2007), tondiite, Cu 3 Mg(OH) 6 Cl 2 (Malcherek et al , 2014) and leverettite (Kampf et al , 2013). The unit cell of these minerals is also analogous to the subcell of paratacamite [Cu 2 (OH) 3 Cl] (Welch et al , 2014).…”