It is a heavy mineral sands slimes sample. Other minerals present include quartz, calcite, clays. I assume it might be some mica, but I have already tried biotite, muscovite, sericite, stilpnomelane.
Dear Mrs. Nauthe,
excluding some strange minerals such as astrophyllite, I think of an Fe-bearing mica in the stage of conversion into hydrobiotite which may attain even d-spacings of higher than 11 Angstroem. It is often the case than minerals with high d-spacings do not show the precise X-ray notations listed in the tables. Hydrated metaforms often significantly differ from the original or primary form. This is not only valid for phyllosilicates but also known from the so-called "U micas" (uranyl phosphates..).
Good luck
H.G.Dill
I'm, as a beginner, using this website to restrict my choices about the suspected minerals; you need the D-spacing of the three main peaks and you should determine the X-ray source used. I hope it will be helpful for you:
http://webmineral.com/MySQL/xray.php#.Ve0Lipcvyew
Regards
Professor Towe...I agree with you. Clay minerals are weakly crystalline materials; they should be separated and specially treated. Did I get what you meant?
Dear Mrs. Naude,
maybe it is not the answer you might expect but if issues are difficult to disentangle as it seems to be the case here I suggest to shift to another method where the readout is clearer and often gives you a clue at least which mineral group it could be. I recommend IR spectrocopy which works very well for hydrosilicates that you suspect in this case. Even if this method is limited to minerals sensitive as being exposed to IR radiation it could bring you a step closer to a solution. If you do not want to use MIR or NIR for preparator reasons or lack of device, try an find somebody who owns a PIMA (portable infrared mineral analizer), a rather common device, which I used very often. Under SWIR you should get an idea which direction the train runs. That is my suggestion to the way out of the dilema.
Good luck
Harald G. Dill
Dear Kenneth,
this is right. Using a settling tube and carrying out a sequential separation from < 63µm downward should even include larger physils such as stilpnomelane and Fe-bearing mica as well as the more exotic smectite-group minerals in the lower particle size. Prior to that a heavy liquid separation with Na polytungstate will do away with quartz and carbonate. So no chemical interaction, which one might expect during chemical treatments, will spoil the mineralogical data collection.
Thanks for the addition.
Best regards
Harald