Mansfieldite

(repeating unit)AlAsO₄·2H₂OIMA symbolMfd^[1]Strunz classification08.CD.10Dana classification40.04.01.04Crystal systemOrthorhombicCrystal classOrthorhombic-Dipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)Space groupPbcaUnit cell876.8 ųIdentificationFormula mass201.93 gmColorWhite, light grayCrystal habitSpherical, encrustationsCleavageIndistinct on {201} and on {001} and {100} in tracesFractureSub-conchoidalMohs scale hardness3.5–4LusterVitreousStreakWhiteDiaphaneityTransparent, transculentSpecific gravity3.03Density3.03Optical propertiesBiaxial (+)Refractive indexn_α = 1.622 – 1.631 n_β = 1.624 – 1.649 n_γ = 1.642 – 1.663Birefringence0.020 – 0.0322V angleMeasured 30°–68°, calculated 38°–82°DispersionNoneCommon impuritiesCobalt

Mansfieldite is an uncommon mineral that was named after an American geologist, George Rogers Mansfield. It has been considered a valid specie since 1948. It is a member of the variscite group. Mansfieldite creates a series with scorodite, and it is the aluminium analogue of said gem. Mansfieldite is colorless in transmitted light.^[2] It is mostly made out of oxygen (47.54%). Other components include arsenic (37.1%), aluminium (13.36%) and hydrogen (2%).^[3] Mansfieldite crystals form due to hydrothermal origin in altered and mineralized andesitic pyroclastic rocks. Due to its size, mansfieldite is hard to see even under a microscope. The pink variation of the mineral is due to cobalt impurities, otherwise it is white to light gray. It can be found in the US, Mexico, France, Algeria, England, Australia, Germany, Algeria and Kazakhstan.^[4]

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