Fettelite

I was loaned 3 specimens for this study:

  1. RWT-12027 Fettelite and Proustite, Nieder-Beerbach, Odenwald, Germany
    lustrous Proustite, and a "sheaf" of flat fettelite blades on calcite.
  2. RWT-12230 Fettelite and Cinnabar, Imiter Mine, Diebel Sarho, Anti-Atlas Mountains, Morocco
    flat sheets of Fettelite, with a dark reddish grey coating. Cinnabar is powdery red (like Minium), with quartz, galena.
  3. RWT-11536 Fettelite, Proustite, Xanthoconite. Imiter Mine, Diebel Sarho, Anti-Atlas Mountains, Morocco
    Cavity in galena with flat plates (hexagonal?) of Fettelite, and nice proustite, and some scruffy xanthoconite.

The rest of this note, I found half finished, with only the plots of the Raman spectra and no text.

All the text you are reading was added just now 11-10-2008 from memory. I will check my notes and add proper text tonight (when I get home where my Raman notebook is).

The first spectra are from the piece from Nieder-Beerbach.
(Hence the "nb" prefix on the filename.)

The first one was a proustite crystal I mistakenly probed.

And here is the fetellite. (I probed the broken edge of a flat blade like crystal on the edge of the specimen).

And here are two spectra from the Imiter Mine piece. I probed two places because the first spectra was so indistinct. (but didn't do any better the second time). Using low power to avoid "scorching" the material, hence the low counts and high noise.

Conclusions

The conclusions are, sad to say, somewhat inconclusive. The spectra are hardly a dead match. Both are a "flat line" with a hump at 200 cm-1. The is more detail on the hump from the Nieder Beerbach material, but I was getting 60 counts rather than 20 overall. I'll check my notes, I may have reduced the laser power to avoid scorching the material. What would I get from equivalent exposures? (This is one of those things that seems clear now, but in the lab, I wasn't paying close attention to being consistent about how long I let the detector integrate). The similarity between the Nieder Beerbach fettelite and the accidental proustite exposure is pretty striking.

So in conclusion, I would say the Imiter material is Fettelite, but that is based more on the visual appearance and the fact that the Raman spectra don't rule it out. But you had already come to this conclusion yourself.

As a curious tidbit: there is a photo on mindat right now of a Fettelite from the Imiter mine listed by Rob Lavinsky -- for what that is worth.

Feedback? Questions? Drop me a line!

Tom's Mineralogy Info / tom@mmto.org