Standards Which Should Be Developed For EPMA

[John Donovan]

As far as Cs is concerned, I'm wondering what is the problem with gem quality pollucite.

Hi Bart,
Well for one thing we are looking for 50 to 100 gram quantities of pure homogeneous material. Now you might reasonably ask: why would we want that much material? And my answer would be: so that every lab on the planet can have more than a "flyspeck" in their standard mounts, so that it can withstand repeated polishing...  Also, for synthesis a tested recipe is necessary in order to avoid creating an entire research project. Do you have a recipe for synthetic pollucite?

I make a Rb bearing silicate glass, but it is a reference material only.  I was quite interested to learn about the Rb,Ti phosphate, and would be willing to buy it at $100 per gram.  Please point me in the direction of the source for that material.

It's here:

http://smf.probesoftware.com/index.php?topic=301.msg2872#msg2872

Please note that this material is not for resale.

[Brian Joy]

A good synthetic or well-characterized natural ilmenite standard would be nice to have.  First, it's a common mineral that needs to be analyzed accurately, especially when trying to ascertain Fe2O3 content.  Second, when I use rutile and hematite as respective Ti and Fe standards, I often get greater than one Ti atom per three-oxygen formula unit.  Overestimation of TiO2 content and underestimation of FeO has been noted by others when using rutile and hematite as standards (see attached paper by Evans et al., p. 152 and appendix).  The errors tend to offset and produce an oxide total near 100% and result in underestimation of Fe2O3 (from charge balance).  Last, the only ilmenite standard available from the Smithsonian is USNM 96189, which is visibly inhomogeneous (see image below) and has an analysis total of only 99.4%.  When I do wavelength scans, I don't see anything other than Ti, Fe, Mn, Mg, and Nb, which are all accounted for in the wet chemical analysis.

Does anyone know if it is relatively easy to synthesize ~100-micron ilmenite crystals, for instance by a reaction such as Fe + Fe2O3 + 3TiO2 = 3FeTiO3 in an evacuated silica glass tube?

Ilmenite USNM 96189: