mawbyite

{{Infobox mineral|boxbgcolor=#c93a0a|image=Mawbyite-177443.jpg|formula=Pb(Fe3+,Zn)2(AsO4)2(OH)2|IMAsymbol=Mby|strunz=08.CG.15|system=Monoclinic|dana=40.02.09.04|class=Prismatic H-M Symbol: 2/m|symmetry=B2/m|unit cell=391.13|molweight=649.02|color=Pale brown to orange-brown to bright reddish brown|habit=Spherical or wheat sheaf shaped crystals|twinning=Common, V-shaped at about {100}|cleavage=Good on {001}|fracture=Conchoidal|mohs=4|luster=Adamantine|opticalprop=Biaxial (−)|refractive=nα = 1.940(2) nβ = 2.000(2) nγ = 2.040(2)|birefringence=0.100|pleochroism=Weak Brown to reddish brown|2V=Measured: 80° (5) Calculated: 76°|dispersion=Relatively weak|length fast/slow=Length-fast|fluorescence=None|streak=Orange-yellow|gravity=5.365|density=5.5|diaphaneity=Transparent to Translucent}}

Mawbyite is a lead iron zinc arsenate that was named in honor of Maurice Alan Edgar Mawby. It has been approved by the IMA in 1988, and was published just a year after being described by Pring. Mawbyite is a member of the tsumcorite group, the monoclinic dimorph of carminite. It was first believed to be tsumcorite; however, crystal-structure determination showed iron and zinc occupying the same crystallographic site instead, and through the analysis it turned out mawbyite is isostructural with tsumcorite, meaning the two share a similar formula. More accurately, mawbyite appears to be the ferric analogue of the aforementioned mineral. The relationship between helmutwinklerite – which shares a similar formula with tsumcorite's – and mawbyite had been suggested, but due to lack of data it remains unclear. A full crystal-structure analysis is required in order to understand the relationship between their structures.