I guess in an ideal world, every lab would use the same standards. That would make the output from different labs better comparable. The standards would be large homogeneous grains with high concentrations of the element of interest and of course beam stable.
Yes, exactly. If we make enough of a standard material, and every lab can obtain that ideal standard for $100 a gram, then maybe every lab in the world *can* use the same standard, at least in these particular places on the periodic table, e.g., Rb.
At the moment, everybody has access to the Smithsonian's, which are available free of charge(?). The problem that I see with these standards is, that most standards are "small" grains. Some are not homogeneous or have inclusions and they are all natural, not synthetic. Larger grains are available to purchase at places like Astimex, P&H, ...
Yes, free fly specks! Our proposal is to instead create enough of a desired synthetic material that is homogeneous, stable and free from inclusions and available for a nominal amount- $100 won't break the bank for anyone! The money Marc will make on these sales will go towards synthesizing the next "crowd sourced" standard.
Ok, back to the ideal world... (@Marc, I will try to convince John) I am not sure, if we need 1kg of material. First of all, most labs are basically broke, because every University wants to do good research, but haven't figured out yet that they need good equipment for that as well (therefore, not every lab will buy all available standards). Second, a lot of labs don't analyses the whole periodic table, but only what the University is "specialized" in. Third, ...
1 kg sounds like a lot but it is an upper limit is the point. It depends on the amount we want to distribute and how may labs are there. Here's our thinking: if we have a few hundred grams of material at least, we we'll be able to offer *everyone* 1 gram splits of the material so you won't have to do with a few fly specs anymore! 1 gm of material should last any lab forever! And how many labs are there? Well let's assume a few hundred EPMA labs, so that's a few hundred grams already.
But what about SEM labs? Shouldn't SEM labs also have standards?
http://probesoftware.com/smf/index.php?topic=302.msg1530#msg1530Adding in SEM labs means we would need 500 or more grams to supply every lab in the world...
Yes, we are starting with Rb and Cs because we already know they are difficult to find good standards for. Let get more suggestions- this is a crowd sourced effort!
I should also mention, these are not intended to be secondary standards that are similar to your unknown matrix. These are intended to be primary standards, which for statistical purposes (see your quant expressions) need to provide the highest x-ray intensity for a given concentration. Usually that means a major amount of the element of interest regardless of matrix. The ideal standard for this? Yes, a pure metal- 99.999% pure of course!
But of course that doesn't work for certain elements, such as Rb and Cs! Hence our synthesis and distribution efforts...
Back to the actual topic, here in Hobart, we do analyse the whole periodic table except for Cs and Rb. 
I guess a standard that we could use is something with Fluorine (ideally large, homogeneous, beam stable, ...). We used to use a Topaz, but we have to replace it and haven't really found a good standard yet. You could use an Apatite or Mica's but they are not beam stable at all. So, to cut a long story short, we are very interested in a Fluorine standard.
I have to wonder if some labs have avoided Rb and Cs simply because they didn't have decent primary standards...?
But, no worries, maybe no one you know is interested in Rb and Cs. We do want to hear what your lab needs. You say, you are interested in fluorine, and that you "used to have" a topaz standard... what happened to it? Did it wander off? Disappear during polishing?
I agree that the apatites and phlogopite are beam sensitive. Tell us, was the topaz beam stable? Was it natural or synthetic? Did it have any OH?
Marc has said that topaz would be easy to grow, but what about the OH molecule?
We are a community of analysts, that cares about EPMA
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