Claringbullite, a new hydrated copper chloride

Abstract

SUMMARY. Claringbullite, Cu4CI(OH)7.nH20 where n is about 0"5, a new mineral, is reported as soft blue plates in cuprite from Nchanga open pit, Zambia and Kambowe, Mina M'sesa, Katanga. The mineral is hexagonal a 6-6708, c 9~I83 A, Z = 2. Optically, claringbullite is uniaxial negative with m = r782 and e = 1"78o. Indexed powder data are given together with five electron-probe analyses of the mineral.IN I973 a specimen of cuprite said to have come from the Nchanga open pit,1 Zambia, with tiny blue platy crystals on one corner, was brought to the Museum for identification by Mr. N. Wilson. The blue crystals were thought to be gerhardtite, Cu2NO3(OH)3 , but their X-ray powder pattern did not correspond to this, or any other known mineral. A match was obtained, however, with a blue mineral from Bisbee, Arizona, belonging to Dr. S. A. Williams. A few days later a blue mineral from the M'sesa mine, Kambowe, Katanga, on loan from the Sorbonne, Paris, and believed to be a new species, was X-rayed and its powder pattern found to be identical with that of the Zambian and Arizonan mineral.The Zambian and Katangan specimens form the type specimens of claringbullite, Cu4Cl(OH)7.nH20 where n is about o'5. The mineral is named for Sir Frank Claringbull, former director of the British Museum (Natural History) and Keeper of Mineralogy. The data that follow and the name have been approved prior to publication by the Commission on New Minerals and Mineral Names, I.M.A. Physical andoptical properties.Claringbullite from Nchanga occurs as a slightly divergent group of blue plates filling a cavity in quartz and malachite on cuprite. Yellow-stained quartz crystals also occur on the specimen. The Katangan occurrence consists of slightly divergent groups of soft blue plates up to I mm across, with pearly lustre, in a vug in cuprite, associated with acicular and tabular crystals of brochantite. Malachite and copper occur elsewhere on the specimen. The claringbullite plates are flattened on {oooI}; cleavage is perfect on {oooI}; distinct on { I oTo} and { 11 ]o}. Fragments from the Katangan specimen were used for the optical investigation and consist of micaceous, thin, delicate laminae with maximum dimensions from o'o5 to 0.28 mm. The mineral is uniaxial negative. In transmitted light it is pale blue with no noticeable pleochroism and coN, is r782 for sodium light. All cleavage flakes remained dark between crossed polars.A cleavage flake of size o.28 x o'I7 x o'oi5 mm was mounted on a stage rotation apparatus. When viewed edgewise it remained pale blue for the principal vibration directions, but it was not possible to determine the refractive index for the extraordinary ray using the immersion method because of the micaceous nature of the fragment. Between crossed polars the edge-on flake showed straight extinction and abnormal interference colours of dark blue rising to yellowishgreen. The yellowish-green interference colour was obtained when the o.17 mm dimensions of the cleavage flake was parallel to the axis of the microscope and was...

Disorder-Induced Structural Complexity in the Barlowite Family of S = 1/2 Kagomé Magnets

“…In the original mineralogical study of claringbullite (FCl), the chemical formula was reported as Cu 4 (OH) 7 Cl•H 2 O. 31 This was subsequently revised to Cu 4 (OH) 6 Cl[Cl 0.29 (OH) 0.71 ], meaning that the 2b site was thought to be occupied by a combination of Cl − and OH − ions rather than F − and that a solid solution of Cu 4 (OH) 6+x Cl 2−x could exist. 32 Following this, exploration into the methods required to synthetically prepare FCl determined that a fluoride source is necessary, and from the structural characterization of synthetic samples, it was concluded that the 2b site was solely occupied by F − based on refinement R-factors.…”

Quantum magnetism in minerals

“…Mineral claringbullite, Cu 4 (OH) 6 FCl [450,451], and its isostructural Br analogue barlowite, Cu 4 (OH) 6 FBr [452,453], crystallize in a hexagonal structure (space group P 6 3 /mmc) in which 3/4 of the Cu atoms on the Cu(1) positions form structurally perfect kagome planes with AA stacking, whereas the remaining 1/4 goes to the Cu( 2) intersites [454][455][456]. More recent studies based on x-ray and neutron diffraction indicate that at low temperatures, high-purity synthetic barlowite undergoes an additional lowering of the crystal symmetry to an orthorhombic structure with either Cmcm [457] or P nma [449,458] space group.…”

Connellite: stability relationships with other secondary copper minerals

“…Claringbullite has a similar mode of occurrence in vughs of cuprite in oxidized copper ore (Fejer et al, 1977). Our synthetic experiments indicate that it is thermodynamically unstable with respect to connellite, at least under the conditions employed.…”

“…To a stirred aqueous solution (100 cm 3) containing CuClz.2H20 (0.725g, 4.25mmol), NaCI (1.6055 g, 27.5 mmol) and NazSO4.10H2 O (0.7 g, 2.2 mmol), CO2-free aqueous NaOH solution (0.05 mol dm -3) was added until the pH of the mixture was 7.2. Fast addition of the hydroxide gave a blue precipitate which recrystallized to connellite within 48 hours if the mixture was kept in a sealed container to exclude CO2, regulated with a thermostat at 25~ X-ray powder diffraction measurements of this transient blue phase showed it to be claringbullite, Cus(OH)14C12.H20, (Fejer et al, 1977), although other amorphous solids may also be present in admixture. The five strongest lines are observed at 5.76, 4.90, 4.60, 2.70 and 2.42A, as compared with literature values of 5.75, 4.89, 4.59, 2.700 and 2.445A.…”