We measured this Raman spectrum on a secondary mineral speleothem of a lava tube (https://www.researchgate.net/publication/265952424_RAMAN_STUDY_OF_SECONDARY_MINERALS_IN_A_RECENT_LAVA_TUBE). The main body was Thenardite and additionaly this spectrum appears occasionaly. Do you know it ?
Thanks for your help.
Conference Paper RAMAN STUDY OF SECONDARY MINERALS IN A RECENT LAVA TUBE
Looks like one of the phases may be a phosphate. The peak at 950 wavenumbers is spot on for the phosphate groups in apatite, although the other apatite peaks seem to be absent or substantially shifted.
Did you run the pattern through CrystalSleuth against the RRUFF database ? If you send me a copy of the spectrum data in CSV format I can run it against a RRUFF extract that is both cleaner and more extensive than the one released with CrystalSleuth from the RRUFF website.
Thanks a lot for your answers !
@ Didier : Sure, it is a nice way to gain information :)
@ Francis and Paul: XRD and SEM-EDX give no presence of any phosphate phase. Only Halite (NaCl), Thenardite (Na2SO4), Aphtitalite (NaK3(SO4)2 and some very small crystals of Potassium Vanadium Oxide hydrate (K4V2O8-3H2O).
Halite has no Raman signature and I assume that the spectrum is the Raman signature of the Vanadate but rruff and bibliographic researches are fruitless.
The spectrum file is linked to this message.
Mr. Guimbretière,
This spectrum has very common characteristic frequencies with this one of topaz. Please find as attachment, but ATR-IR of topaz. So that it would be silicate.
Mr. Guimbretière,
In addition to above shown ATR-IR of topaz, please find a Raman spectrum of the same mineral, found in Tepetate (Mexico), measured at lex = 514 nm. There really have very common characteristic frequencies with your sample.
You could pay attention, too, on the Raman spectra database, from where originates the shown here Raman spectrum (http://rruff.info/). There have abailable samples from different regions and a representative set of minerals, measured at different lex, which would be helpful to identify your substance.
As expected running a spectrum match against the RRUFF spectra did not produce a good match. However, the best match was with a Fairfieldite which showed a positive match to the two strongest peaks. This does lend some support to the concept that your unknown may be a phosphate. Since your SEM-EDX data does not support this it may be worth the effort to attempt to get SEM-EDX data on the exact region that this Raman spectrum was taken from.
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