Standards Which Should Be Developed For EPMA

[John Donovan]

I'm interested in developing (or obtaining) a synthetic topaz for general distribution to the community,  but I'm curious if this mineral can exist without any OH.  Does anyone know?  Specifically I'm wondering if an end member topaz such as Al2SiO4F2 as opposed to Al2SiO4(F,OH)2 might be possible, since both F and OH are -1 valence, and also might be more beam resistant...

We all know that fluor-phlogopite is problematic because when mounted in epoxy it separates into very thin lamellae and fluor-apatite is very beam sensitive, so a synthetic pure topaz might be very useful, but is there any reason one couldn't use topaz as a standard for silicate characterization?  I mean, are there peak shape or shift issues when using topaz as a fluorine standard for say amphiboles or biotites?
john

[Probeman]

According to the attached paper (provided by Prokopiy Vasilyev), natural topaz can contain little or no OH.

Does anyone have any ideas or suggestions on who we might contact, that might have ideas on obtaining such as synthetic topaz for use as a F standard?

[Anette von der Handt]

So I found this old, old paper about synthesizing anhydrous topaz (see attached). It comes out of the Washington State Lab so maybe we can have Owen hunt around if there is a jar of it (hahaha) standing around.

The paper gives some info on how to synthesize it and it needs a cold seal pressure vessel which we don't have here. However, it sounds that the experiments were quite lengthy and did not result in large grains necessarily.

Bernd Wunder at GFZ Potsdam synthesized OH-rich Topaz which is not what you are looking for. He may be the person to talk to nevertheless?

[Probeman]

Marc was trying to grow CsZrOPO4 but got CsZr2(PO4)3 instead.  That means to me that CsZr2(PO4)3 is "easier" to synthesize than the other.  But what do I know?

I got this info back from our crystallographer on the Cs material that Marc grew as a test case for us:

It was expected as CsZrOPO4. Based on the X-ray structure it is Cs O12 P3 Zr2. The structure of the compound with the same formula was determined and published before as trigonal. This crystal is orthorhombic and seems to be different phase.

So "Cs O12 P3 Zr2" is also what I got from EPMA (CsZr2(PO4)3).

Attached below is his CIF file in case anyone is interested. 

[Probeman]

I recently made an official request for an agenda item at the next M&M this summer to Tom Kelly regarding MAS support of standard material development for the SEM/EPMA community. Here is my letter:

Hi Tom,

Ed Vicenzi suggested I request an agenda item on the possibility of the MAS society funding standard materials development for the next council meeting. Unfortunately I will not be attending the M&M conference this year.  So I would like for you to present this as described below. I am aware that the FIGMAS group is already consolidating information on existing standards, but I feel that we do not need a year of study to realize that we have serious deficiencies in our standards for some critical elements (e.g., alkali metals, halogens, etc.). I propose:

1. The technique of x-ray emission quantification depends on high quality and sufficient quantities of standard materials. This is particularly true for WDS and I would argue for EDS as well (delete the standardless button!).

2. Most standard materials available from traditional sources (the Smithsonian for example), are natural materials with well documented issues of inclusions and variable composition, and are available only in "fly speck" quantities. Commercial standards are expensive and also problematic for similar reasons.

3. Today, synthetic single crystals of high purity (all traces below detection limits) that are stoichiometrically constrained by thermodynamics, can be produced in 0.1 to 1.0 kilogram quantities quite easily by those with expertise. Thus relieving us of the problems with "fly speck" quantities and variable compositions and/or inclusions in our standard materials. Every EPMA/SEM lab in the world should have a gram of these materials.  Then we are all "on the same page" so to speak...

3. We have demonstrated that an ideal (beam stable, insoluble, stoichiometric and high purity), standard for Rb (RbTiOPO4), can be synthesized and is *already* available to all at $100/gram (such as deal). See here for details:

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

4. A effort to identify further possible candidates for synthesis has begun here (you must be logged in to see the poll results):

http://probesoftware.com/smf/index.php?topic=560.0

The current winner by popular demand is a cesium zirconyl phosphate which would be beam stable, insoluble in water and stoichiometric. A quotation from one synthesis firm will give the society 50 grams of material for $5K (or 100 grams for $10K).  In other words we can break even on our investment at $100/gram!  I don't really care where/who distributes these "community standards", but I think we need to start a program to begin this process even if it is one lonely standard material at a time!

5. A good use of the society's money is student support and decent food, but I would argue that standard development efforts are a seriously neglected area for a society whose flagship method (EPMA/SEM) is entirely dependent on high quality and readily available standards. As NIST will only produce glasses which are compositionally problematic (how do we know what we just made, and is it homogeneous?), single crystal synthesis seems a worthy cause to add to the society's mission.

What can we do to advance this agenda? I would be happy to discuss this by phone.  Thanks for your support.

john

Here is Tom's reply:

Hi John,
This is an excellent idea and I thank you for advocating. I will indeed put this on the agenda and yes, please feel free to publicize this issue. I agree with your arguments.

We mainly will need to be sure that the finances and logistics work out and I assume that others in the community will agree with the sentiments you express here.
I will present this at Council.
Keep me informed.
Regards,
Tom

Comments/suggestions?

[John Donovan]

Here is Ed Vicenzi's response to my MAS council agenda item request:

Tom and John

 I am happy this item will make its way on to the MAS summer council agenda. I would however advise that if this measure is adopted by the council that a discussion/survey monkey  take place to ensure that the first MAS-subsidized material synthesized represents a priority community need. I understand there has been some prior discussion, but for many this will be the first time they have heard of the topic.

 Cesium zirconyl phosphate has it's virtue as a selection, but it may not represent a community priority.  Anecdotal I know, but during my own decades long career I have been engaged in exactly a single instance when Cs was an important part of a system of research interest.  In a recent telephone discussion with John Donovan he mentioned that he did not care which material was synthesized for this purpose, only that the society should be involved in standard synthesis as a way of investing in/engaging the MAS membership.  I want to see this happen, but I don't want to have Cs zirconyl phosphate produced as the first MAS-funded material if their are other more pressing needs, whatever they may be.

Ed

My response was :

I agree completely.   Personally I'd prefer an end-member fayalite. Let's see what a survey says.

To which I would add: or a fluor-topaz synthetic!   

Frankly, any "community sourced" standard material (broadly available), would be an improvement over what we have currently. I realize that there are commercial sources for standard materials, and many of these are fine, though not inexpensive. Likewise we have several non-profit materials available, but generally only in tiny quantities.

Maybe Cs isn't the best candidate standard material to develop first, though I would argue that we already know there is no broadly available, beam stable, non water-soluble,  stoichiometric material currently available at the moment for Cs.  And we have a recipe for its synthesis...

Yes, let's perform a MAS (sanctioned) survey of the next standard material that should be developed (as a community), and observe the consensus priority. How do we start that survey process (as a society)?  I assume the MAS council would have to request such a survey...

[Probeman]

Ed Vicenzi sent me this link which contains the recipe for synthetic fayalite:

http://www.minsocam.org/ammin/AM65/AM65_381.pdf

Marc and Mark: does this seem a feasible synthesis for your labs?

[Marc Schrier]

Hey John (and Ed),
   Unfortunately neither myself or Mark are set up to do a Czochralski (Giant Crystal Growth).  We're more accustomed to smaller crystals, and could potentially utilize the same conditions as a Czochralski growth without the sophisticated rotating and pulling apparatus.  In this case, while the conditions (temp, pressure, gas, etc) are very doable, the flux is less than ideal for the way we tend to work.  With FeO (reduced from Fe2O3) and SiO2 as the two ingredients, it would be difficult to isolate the Fayalite (Fe2SiO4) from the flux (maybe there is a sweet spot for an acid).  More ideally we look for water soluble salts like the alkali halides and phosphates we can decant and then wash away from the crystals.  Maybe it's worth pinging the authors to see if they have any old samples.
-Marc

[Probeman]

Hey John (and Ed),
   Unfortunately neither myself or Mark are set up to do a Czochralski (Giant Crystal Growth).  We're more accustomed to smaller crystals, and could potentially utilize the same conditions as a Czochralski growth without the sophisticated rotating and pulling apparatus.  In this case, while the conditions (temp, pressure, gas, etc) are very doable, the flux is less than ideal for the way we tend to work.  With FeO (reduced from Fe2O3) and SiO2 as the two ingredients, it would be difficult to isolate the Fayalite (Fe2SiO4) from the flux (maybe there is a sweet spot for an acid).  More ideally we look for water soluble salts like the alkali halides and phosphates we can decant and then wash away from the crystals.  Maybe it's worth pinging the authors to see if they have any old samples.
-Marc

I spoke with Lynn Boatner (not a co-author but involved with the project I think), about 5 years ago and at that time he told me the gram or so of Fe2SiO4 he sent me was the last piece at the lab. Besides which we would ideally like to produce 50 to 100 grams (or more!) for the community for the  future.

Please remember, the idea with these potential standard materials is *not* to do a "one off" synthesis for a published paper, but rather to produce a significant quantity of pure stoichiometric material for distribution to the EPMA and SEM communities as primary standards.

That's why finding a commercial grower is the first step, but after not finding these materials in quantity on the market I hoped a custom synthesis lab such as yours or Mark's could be an alternative.

That is if we can get the Microbeam Analysis Society to make the necessary financial investment. Mark quoted $5K for 50 grams of the Cs zirconyl phosphate, so that is the sort of things we are interested in.
john

[Jeremy Wykes]

Synthesis by optical floating zone furnace is another option. Some colleagues from RSES have been successfully making single crystal Fo90 under controlled atmosphere.

[Probeman]

Synthesis by optical floating zone furnace is another option. Some colleagues from RSES have been successfully making single crystal Fo90 under controlled atmosphere.

Hi Jeremy,
I know that pure Mg2SiO4 is commercially available, but I've never seen pure Fe2SiO4. Could this method be used to synthesize end member fayalite? 

The nice thing about end-members is that once you have one, you already know it's exact chemistry.   
john

[Jeremy Wykes]

End-members are much easier to make via floating zone than intermediate compositions. I suspect floating zone fayalite is not common due to the need for controlled atmosphere. Liebenbergite and Co2SiO4 could be made the same way, possibly also willemite and tephroite.

[Probeman]

A dissertation from RWTH describing a procedure for Co-olivine synthesis, possibly germane to this discussion.

http://publications.rwth-aachen.de/record/50831/files/Sazonov_Andrew.pdf

Or at least german to the discussion!   
john

[Bart Cannon]

I've been selling standards, or more correctly "reference materials as a little sideline business since 1993.  They are mostly single crystal natural minerals and I have nearly a thousand different materials, and many materials from multiple locations.  Hundreds of classic locations are included in my inventory.  Topaz, for example, is present in my stock from at least a dozen localities.  I have all of Gerald Czmanske's (formerly of the USGS) sulfides and tellurides that he synthesized very carefully in hydrogen fused quartz tubes.  Some have two phases so the actual stoichiometry is sometimes questionable.

At one time I listed all of these on my old Frontpage website, but when every host dumped Frontpage support, I never re-built my website.  I am however, slowly rebuilding that site.  If you are desperated for something, you are welcome to contact me.  Standards suppliers are not happy with me since I sell them at reasonable prices (mostly $15 ea for a 400 uM grain).

As far as Cs is concerned, I'm wondering what is the problem with gem quality pollucite.  I have galkaite and rhodizite in addition to 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.

New minerals and re-classification of existing species via hair splitting end member assignments is making it nearly impossible to stay current with IDs.  Check Mindat.org and Webmineral.com for current descriptions of minerals new and old.  Mineral people never use the term "apatite", for example.  Apatite "group", sometimes, but the fastidious use carbonate apatite, fluorapatite and hydroxyl apatite.  I have well identified examples of each.  Cannonite is named for yours truly.  I have five other new minerals that I brought to the mineral world.

Bart Cannon / Cannon Microprobe / Seattle

[Bart Cannon]

By the way, the OH analog of topaz has yet to be named by the International Mineralogical Association.