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

ABSTRACT Keystoneite (IMA87–049) 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)3·4H2O. 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,Å(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) Å, c = 7.6173(3) Å, V = 578.77(6) Å3, 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”.

Modeling on-site wastewater treatment system performance fragility to hydroclimate stressors

Increasing variability of climate-related factors, especially precipitation and temperature, poses special risks to on-site wastewater treatment systems (OWTS), which depend on subsurface saturation conditions for treatment and dispersion of wastewater. We assess OWTS fragility – the degree to which a system loses functionality – as a step to characterizing the resilience of residential wastewater treatment systems. We used the frequency and indexed severity of OWTS failures and resulting repairs to quantify fragility as a function of hydroclimate variables, including precipitation, temperature and stream flow. The frequency of each category of repair (minor, moderate and major) for 225 OWTS obtained from Boulder County public health records was modeled as a function of climate factors using a generalized linear model with a Poisson distribution link function. The results show that prolonged precipitation patterns, with monthly rainfall >10.16 cm, influence OWTS fragility, and complete loss of OWTS functionality, requiring replacement, is impacted by high temperatures, frequency of wetter-than-normal months, and the magnitude of peak stream flow in the watershed. Weather-related covariates explained 70% of the variability in OWTS major repair data between 1979 and 2006. These results indicate that fragility arising from climate factors, and associated costs to owners, environmental and health impacts, should be considered in planning, design and operation of OWTS.