A couple of weeks ago, I had a user ask me if I had a vanadium silicate standard that wasn't a glass like the old standards from the University of Oregon. To my knowledge, there still isn't a commercially available vanadium silicate standard. In lieu of not having the equipment to try and grow my own material, I got to thinking about what we might be able to use for such a material. In the end, I decided to test out some cavansite, CaVSi4O11*4(H2O), a modulated layer phyllosilicate. There is quite a bit of this material available on ebay and through other sources that actually comes from the type locality in India.
I received two ~1 cm balls of the material for $20. I was actually quite amazed to find that it is extremely clean. At most, I found maybe three or four 20-40 µm grains of quartz in the material that I disaggregated for analysis (~1/2 a ball). Once I mounted up the material and got it in the probe, I was even more surprised at just how clean it is. Aside from the quality of my quick polish, there appears to be no real evidence for zoning or inclusions throughout the sample (see attached SE image). As well, a couple of element maps revealed no apparent zoning (see element map attachment).
So far, I have put down 74 analyses across 16 grains in the sample and everything has been really homogeneous. The results are summarized below:
AccV 15.0
Curr. (nA) 20.0
Ox = 22
Avg STDV min max WebMineral
V2O5 20.138 0.702 18.588 22.123 20.15
MgO 0.242 0.116 0.061 0.445 -
SiO2 53.146 1.239 51.159 55.272 53.24
CaO 11.998 0.312 11.185 12.42 12.42
Total 85.696 1.343 83.221 87.946 85.81
I am pleasantly surprised with the results thus far. Element mapping before and after analysis reveals no obvious beam mobilization of the elements. The beam does cause a bit of damage to the specimen, however, the damage is not apparent in the post-analysis element maps. The lack of any zoning after the analysis would suggest to me that the specimen is just locally dewatering around the analysis spot and damaging the carbon coat (see attached beam effect.png). This should be expected as the mineral is a phyllosilicate.
Anyways, I am curious to see what everyone else thinks about the potential of cavansite as a V-silicate standard. If enough people are interested, then I'd be more than willing to send around some of the material for a "round-robin" test. There is plenty of it to go around.