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Crystal Chemistry of Zemannite-Type Structures: III. Keystoneite, the Ni2+-Analogue of Zemannite, and Ferrotellurite Discredited


Missen, OP and Back, ME and Mills, SJ and Roberts, AC and LePage, Y and Pinch, WW and Mandarino, JA, Crystal Chemistry of Zemannite-Type Structures: III. Keystoneite, the Ni2+-Analogue of Zemannite, and Ferrotellurite Discredited, The Canadian Mineralogist, 59, (2) pp. 355-364. ISSN 1499-1276 (2021) [Refereed Article]

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PDF (Full description of new mineral keystoneite (never previously published) and discreditation of ferrotellurite.)
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DOI: doi:10.3749/canmin.2000009


Keystoneite (IMA87049) is a tellurite mineral from the Keystone mine, Magnolia District, Boulder County, Colorado, USA. In this paper the first full description of keystoneite is presented. Keystoneite is the Ni2+ analogue of zemannite and has the ideal zemannite-like formula of Mg0.5Ni2+Fe3+(Te4+O3)34H2O. The chemical composition via electron-probe micro-analysis (in wt.%; standard deviations in brackets) is Na2O 0.3 (0.2), K2O 0.1 (0.0), MgO 4.3 (0.3), Mn2O3 1.1 (0.7), Fe2O3 5.1 (1.2), NiO 12.7 (1.7), and TeO2 65.5 (0.7). H2O was determined by TGA analysis, giving 15(3) wt.% H2O, however, H2O from the structural determination gave 10.0 wt.%, the latter giving an analytical total of 99.1 wt.%. Keystoneite crystallizes in the non-centrosymmetric space group P63. The six strongest observed powder-diffraction lines [d,(I)(hkl)] are 8.12(90)(100), 4.05(80)(200), 2.952(50)(112), 2.838(50)(121,211), 2.774(100)(202), and 1.720(60)(204). The unit-cell parameters determined from single-crystal X-ray diffraction are a = 9.3667(5) , c = 7.6173(3) , V = 578.77(6) 3, and Z = 2. Keystoneite was first identified from a specimen of "ferrotellurite", a mineral with the reported formula Fe2+Te6+O4. The discreditation of "ferrotellurite" has been accepted by the IMA-CNMNC, Proposal 19-G, as no material corresponding to a phase remotely similar to Fe2+Te6+O4 was found on any historical samples labelled as containing "ferrotellurite".

Item Details

Item Type:Refereed Article
Keywords:keystoneite, new mineral, zemannite, tellurite, microporous, ferrotellurite, discreditation
Research Division:Earth Sciences
Research Group:Geology
Research Field:Mineralogy and crystallography
Objective Division:Mineral Resources (Excl. Energy Resources)
Objective Group:Other mineral resources (excl. energy resources)
Objective Field:Other mineral resources (excl. energy resources) not elsewhere classified
UTAS Author:Missen, OP (Dr Owen Missen)
ID Code:154966
Year Published:2021
Deposited By:CODES ARC
Deposited On:2023-01-20
Last Modified:2023-01-25

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