#NewPaper alert! After four decades, we finally determined the structure of fairbankite! Being a mineralogist is very like being a detective, looking for micron-scale clues and trying to separate overlapping peaks in SEM-EDX (sulfur and lead, grrr). 1/7
https://doi.org/10.2138/am-2020-7536

The full paper is available online here. Send me a DM if you'd like the PDF! 2/7
https://hes32-ctp.trendmicro.com:443/wis/clicktime/v1/query?url=https%3a%2f%2fpubs.geoscienceworld.org%2fmsa%2fammin%2farticle%2f106%2f2%2f309%2f594219%2fElucidating%2dthe%2dnatural%2dsynthetic%2dmismatch%2dof%2dPb2%3fguestAccessKey%3dc56b9880%2d20e9%2d426d%2da59e%2dcddfee4bce1d&umid=30fb4fa1-6a7b-49f4-a9e7-65d42c6115ea&auth=89a422ce48cf9afc268cabe806cc53ea452e36bd-9ea9699f9178f784c81e5e09b7799ad82720f5dbhes32-ctp.trendmicro.com/wis/clicktime/

Fairbankite had the formula of PbTeO3 - simple, right? But no crystal structure to back this up. 35 years of searching for fairbankite crystals yielded only cerussite, PbCO3. The writing was on the wall for fairbankite...
https://www.mindat.org/photo-1034149.html
Here's a (prettier) cerussite! 3/7

...but #MikeRumsey of the @NHM_London carefully researched all possible type specimens of fairbankite and found some Pb-Te-O crystals using whole-rock SEM. We extracted these from the specimen for SXRD and EPMA work. 4/7

The crystal structure showed that there isn't just Pb, Te and O in the mineral - but also S! The S was swamped in the Pb peak of the EDX during whole-rock work. Careful EPMA work showed 1.6 wt% SO3 in fairbankite! 5/7

Structure is a unique framework of PbOn polyhedra with TeO3 pyramids and TeO4 'seesaws'. 1 in 12 of the Te sites is replaced by SO4 tetrahedra, creating an extra layer of complexity. Unique in chemical composition and in structure, fully described 4 decades after discovery! 6/7

Collaboration team across @museumsvictoria , @monasheae , @NHM_London , @NHMLA , @tuvienna and @univienna ! 7/7

Any questions / comments, do let me know :)