Author Topic: Amelia Albite values  (Read 731 times)

BenjaminWade

  • Professor
  • ****
  • Posts: 192
Amelia Albite values
« on: July 08, 2019, 09:38:24 pm »
Hi all
Simple question, but I was wondering if anyone would be kind enough to let me know what values they are using in their Standard file for Amelia Albite? I have a couple of pieces, one in an old Taylor mount and one in and old P&H mount. I have been using the one in the Taylor mount for a long time now, and was using the following values:

St  735 Albite - Taylor Mount
ELEM:        O       Na2O     Al2O3    SiO2        K2O     CaO
OXWT:     .003    11.458   19.764   68.139    .229    .378
ELWT:    48.700   8.500    10.460   31.850    .190    .270

These match what is on the SPI website.

The other day I decided to start using the Amelia Albite in my P&H mount and noticed that the reference values given in the P&H handbook are different:

St  900 Albite - P&H mount
ELEM:     SiO2     Al2O3    Na2O      K2O        O
OXWT:   68.673  19.499  11.741    .133    -.046
ELWT:    32.100  10.320   8.710     .110   48.760

Of course both the Taylor and P&H values magically total to 100. In addition the P&H reference doesn't give Ca even though it is present in there. Also note large difference in Si values.

I have been using the Taylor mount and Taylor values for some time now and has seemed to be ok. If I use the Astimex Albite (Strickland Quarry, Ct) to analyse the P&H Amelia albite, I get Si and Al values more in line with the Taylor values (Si - 68.08 and Al 19.90).

Cheers

Probeman

  • Emeritus
  • *****
  • Posts: 2066
  • Never sleeps...
    • John Donovan
Re: Amelia Albite values
« Reply #1 on: July 09, 2019, 10:31:03 am »
Hi all
Simple question, but I was wondering if anyone would be kind enough to let me know what values they are using in their Standard file for Amelia Albite? I have a couple of pieces, one in an old Taylor mount and one in and old P&H mount. I have been using the one in the Taylor mount for a long time now, and was using the following values:

St  735 Albite - Taylor Mount
ELEM:        O       Na2O     Al2O3    SiO2        K2O     CaO
OXWT:     .003    11.458   19.764   68.139    .229    .378
ELWT:    48.700   8.500    10.460   31.850    .190    .270

These match what is on the SPI website.

The other day I decided to start using the Amelia Albite in my P&H mount and noticed that the reference values given in the P&H handbook are different:

St  900 Albite - P&H mount
ELEM:     SiO2     Al2O3    Na2O      K2O        O
OXWT:   68.673  19.499  11.741    .133    -.046
ELWT:    32.100  10.320   8.710     .110   48.760

Of course both the Taylor and P&H values magically total to 100. In addition the P&H reference doesn't give Ca even though it is present in there. Also note large difference in Si values.

I have been using the Taylor mount and Taylor values for some time now and has seemed to be ok. If I use the Astimex Albite (Strickland Quarry, Ct) to analyse the P&H Amelia albite, I get Si and Al values more in line with the Taylor values (Si - 68.08 and Al 19.90).

Cheers

Hi Ben,
I think both compositions could be roughly "correct".  Why do I say this?  I suspect the situation is similar to the infamous San Carlos olivine which has been shown to exhibit a range of compositions as documented by John Fournelle and others:

https://www.cambridge.org/core/journals/microscopy-and-microanalysis/article/an-investigation-of-san-carlos-olivine-comparing-usnmdistributed-material-with-commercially-available-material/29A60B5E119773D4C144B13259607552

It turns out that if one goes to San Carlos, New Mexico and scrounges around, one can pick up pieces of what might be called "San Carlos olivine".  All with a variety of compositions!

I've heard similar things about Amelia albite. That is, someone goes to the Amelia courthouse in Virginia, picks up some pieces of feldspar, calls it "Amelia albite" and distributes it as such. 

Problem is, it's a natural material and it is not exactly consistent in composition. I'm not going to rant on about how we shouldn't be using naturally sourced standard materials, but suffice to say, I think this is part of the reason we can't get our standards to agree with each other.
« Last Edit: July 09, 2019, 11:26:36 am by Probeman »
The only stupid question is the one not asked!

crystalgrower

  • Professor
  • ****
  • Posts: 43
Re: Amelia Albite values
« Reply #2 on: September 04, 2020, 07:01:34 am »
I have seen the "raw" Amelia Albite that Dr. Charles Taylor had in his stash.  It is a clear phase intergrown with an opaque colourless phase.  No way I would personally choose this as a "primary" calibrator.  I was always told that there was beam induced Na drift...I think a synthetic high temperature-high pressure mineral would be a better "primary" calibrator.  No?

Probeman

  • Emeritus
  • *****
  • Posts: 2066
  • Never sleeps...
    • John Donovan
Re: Amelia Albite values
« Reply #3 on: September 04, 2020, 09:14:10 am »
I have seen the "raw" Amelia Albite that Dr. Charles Taylor had in his stash.  It is a clear phase intergrown with an opaque colourless phase.  No way I would personally choose this as a "primary" calibrator.  I was always told that there was beam induced Na drift...I think a synthetic high temperature-high pressure mineral would be a better "primary" calibrator.  No?

I agree with crystalgrower completely.  These natural materials with their inclusions, beam instability and heterogeniety might have been the best we could do 20 or 40 years ago, but if (for example) we consider that what people call "San Carlos Olivine" in their standard collections is actually a distribution of compositions, as documented by John Fournelle, it seems to me that we are living in the "pre-enlightenment" period of microanalysis. That is, analogous to before we had a global meter and kilogram standard.  This is intolerable.

We (as professional scientists) need to start a global effort to create high purity, synthetic stoichiometric standard materials in the hundreds of gram quantities, so that every SEM/TEM and EPMA lab in the world has access to primary standard materials that we *know* are exactly the same.

Only then perhaps, can we begin a "consensus" k-ratio database.   I propose starting with high purity MgO, high purity Al2O3 and high purity MgAl2O4 synthetic materials grown in several hundreds gram quantities.  From this we can obtain two k-ratio measurements (Mg ka in MgAl2O4/MgO and Al Ka in MgAl2O4/Al2O3) from every microanalysis lab in the world. Then we would actually be doing modern global science.

There are many other suitable materials that would qualify for such "global primary standard" status, e.g., Mg2SiO4, SiO2, etc.

Just my 2 cents.
« Last Edit: September 04, 2020, 09:37:57 am by Probeman »
The only stupid question is the one not asked!

crystalgrower

  • Professor
  • ****
  • Posts: 43
Re: Amelia Albite values
« Reply #4 on: September 09, 2020, 06:22:38 am »
John, this scientific approach has three components:

A: How to Get The Stuff  ALL these materials are available in 99.999 or higher purity in bulk with certificates of analysis

MgO from Alfa Aesar

Al2O3 from Atomergic Chemetals Corp

MgAl2O4 from Crystran Technologies

SiO2 from various including Alfa and affiliates like Johnson Matthey

TiO2 from  NL Industries

SrTiO3 from Atomergic Chemetals; also Si and SiC, CaMoO4, BaTiO3, Y3Al5O12 etc

These items in high purity form are already included in several brands’  commercial “mineral” mounts.

The only simple oxide that I did not find a source for is crystal SnO2.  Natural clean pure SnO2 is extremely rare in collections.   Black “cassiterite” has so much Fe that it approaches FeSnO3.   The sintered material has the bad habit of absorbing oil from polishing media.

The priority synthesis need is for a beam stable Na phase.   We have both  fluxed and hydrothermal syntheses of NaScSi2O6 from  Jun Ito (see attached pdf). 

B: Software

A built-in or downloadable package data collection sequence that can be used with a commercial  calibrator suite to run a sequence of measurements.  I specifically ask for the format where an operator can run this sequence and export data without changing the internal calibration database on their instrument.   Because people get really, really attached to their  set routines.

C: A need to calibrate some stuff between some ears

Knowledge of the science of calibration is a very separate issue from running a probe.  (or an AA or EA or IRMS or HPLC or any other instrument)   

This science is usually covered in “instrumental methods of analysis” late-stage undergraduate chemistry honours/specialist coursework.   I have met a few geologists who were encouraged to take this and the corresponding graduate chemistry course (usually called “advanced analytical chemistry”).  If you have mastered all available coursework starting with “wet methods of chemical analysis” and proceed through these other two courses, then you are prepared to create and validate a new analytical protocol, regardless of which method or instrument you are required to use.  Probe operators who are university employees can audit all these courses and any prerequisites. 

I was  berated by one  “probe operator” because the  fluorapatite F data I was selling  “was wrong”.  My data most certainly did not agree with data from their F-ap grain that had been in routine use for 10+ years.  That grain started out as 3.7%F  and had gone to 9%F but of course the only possible interpretation was that I was “selling wrong data”.   I emailed the relevant RIMG chapter with a simple sentence “this information might be helpful” and the operator’s supervisor accused me of “harassment”.   Having free access to excellent materials and world class chemistry professors was not enough.

I think we need a new thread after this. 
« Last Edit: September 09, 2020, 09:14:34 am by John Donovan »

Probeman

  • Emeritus
  • *****
  • Posts: 2066
  • Never sleeps...
    • John Donovan
Re: Amelia Albite values
« Reply #5 on: September 09, 2020, 05:55:19 pm »
MgO from Alfa Aesar

Al2O3 from Atomergic Chemetals Corp

MgAl2O4 from Crystran Technologies

SiO2 from various including Alfa and affiliates like Johnson Matthey

TiO2 from  NL Industries

SrTiO3 from Atomergic Chemetals; also Si and SiC, CaMoO4, BaTiO3, Y3Al5O12 etc

These items in high purity form are already included in several brands’  commercial “mineral” mounts.

I agree these items (and other similar materials) should be a priority for our microanalysis societies to make a significant global investment in.  If we're actually serious about accuracy that is!   :)

The priority synthesis need is for a beam stable Na phase.   We have both  fluxed and hydrothermal syntheses of NaScSi2O6 from  Jun Ito (see attached pdf). 

I did not know about this material. Very interesting.
The only stupid question is the one not asked!