When Thora Met Molly

Back in February 2016 we created a short blog "Pull Your Fingerite" about a BBC article (and others) covering a paper by Dr Robert Hazen, of the Carnegie Institution in Washington DC, and Prof Jesse Ausubel of The Rockefeller University, in New York published in the American Mineralogist journal.

This was to unveil the work done to create a list of the 2500 rarest mineral species on Earth.

The article concludes with a SEM image of a mineral captioned "Ichnusaite: Contains the radioactive element thorium and lead-like molybdenum, with only one specimen ever found, in Sardinia".

Of course time and discoveries (and terms of reference) move on and although ichnusaite is an exceptionally rare mineral endemic to Su Seinargiu, Cagliari Province, Sardinia, Italy there is more than one specimen, albeit only distinguishable from its close relative nuragheite by electron microprobe analysis.
 

Ichnusaite and nuragheite are identical barring the count of included water atoms - hydration, see table.

The minerals are in an exclusive group of actinide molybdates, and the first and only natural thorium molybdate species.

The bismuth/molybdenum locality at Su Seinargiu is a very rich source of rare and endemic minerals, according to Mindat there are 66 recorded species, of which 8 have been discovered there. e-Rocks is doing ok with 7/8 of these species recorded in our database.
 

Only one more sticker to complete the set - though I think it might be some time before someone finds a specimen of cabvinite big enough to photograph by conventional means!