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Kernowite, Cu2Fe(AsO4)(OH)4⋅4H2O, the Fe 3+ -analogue of liroconite from Cornwall, UK

DOI: 10.1180/mgm.2021.40 DOI Help

Authors: M. S. Rumsey (Natural History Museum) , M. D. Welch (Natural History Museum) , J. Spratt (Natural History Museum) , A. K. Kleppe (Diamond Light Source) , M. Števko (Earth Science Institute, Slovak Academy of Sciences; National Museum, Cirkusová)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Mineralogical Magazine

State: Published (Approved)
Published: May 2021

Abstract: The occurrence, chemical composition and structural characterization of the new mineral 3+ kernowite, ideally Cu2Fe(AsO4)(OH)4·4H2O, the Fe3+ -analogue of lirconite Cu2Al(AsO4)(OH)4·4H2O, are described. Kernowite occurs on specimens likely sourced from the Wheal Gorland mine, St Day, Cornwall, U.K in the cavities of a quartz-gossan rich in undifferentiated micro-crystalline grey sulphides and poorly crystalline arsenic phases including both pharmacosiderite and olivenite group minerals. The average composition of kernowite determined from several holotype fragments by electron microprobe analysis is Cu1.88(Fe0.79Al0.09)Σ0.88(As1.12O4)(OH)4·3.65H2O. The structure of kernowite has been determined in monoclinic space group I2/a (a non-standard setting of C2/c) by single-crystal X-ray diffraction to R1 = 0.025, wR2 = 0.051, Goodness-of-fit = 1.112. Unit-cell parameters from SCXRD are a = 12.9243(4)Å, b = 7.5401(3)Å, c = 10.0271(3)Å, Beta = 91.267(3), V = 976.91(6)Å3 (Z = 4). The chemical formula of this crystal indicated by SCXRD from refined site-scattering is Cu2(Fe3+0.84(1)Al0.16)AsO4(OH)4·4H2O. The network of hydrogen-bonding has been determined and is similar to that reported for liroconite from Wheal Gorland by Plumhoff et al. (2020).

Subject Areas: Earth Science, Chemistry

Diamond Offline Facilities: Raman Microscope (HORIBA Jobin Yvon LabRAM HR 800 Dual Microscope)
Instruments: NONE-No attached Diamond beamline

Added On: 22/05/2021 11:59

Discipline Tags:

Earth Sciences & Environment Geology Mineralogy Geochemistry

Technical Tags:

Diffraction X-ray Powder Diffraction