Well I don't have a beam, just Am241 buttons. So I guess that will have to wait until I get a real x-ray source.
El El lun, ene. 20, 2020 a la(s) 9:19 p.?m., WILLIAM S Dubyk < sdubyk@...> escribi¨®:
You would have to get the tightest beam focus possible then zap the mineral from a variety of angles. Try that and see what you get, that might be interesting.
So would I be able to see anything one way or another with my Si-PIN?
El El lun, ene. 20, 2020 a la(s) 9:06 p.?m., WILLIAM S Dubyk < sdubyk@...> escribi¨®:
I'm sure they are Charles, for sure the ones from the South Platte peg area, those are probably intergrown with thorite, both are tetragonal and exsolve after a certain point. But it is hard to find detailed analyses of those. I suspect the Llano cyrtolites
are like that too, maybe Frank has some good analyses of those. Cyrtolites are formed during a late stage so they likely are all pretty messy, a conglomeration of several rare minerals.?
Steve
Steve, I don't understand everything you said but are any of my cyrtolites examples of this?
Charles
El El s¨¢b, ene. 18, 2020 a la(s) 10:09 p.?m., Dude < dfemer@...> escribi¨®:
Steve,
Zircon HREE¡¯s are interesting. Why do the heavies kick up in the xenotime.? Are there other zircons in the area that still hold the HREE without any exsolution and at what concentration??
How many episodes of mineralization have these materials been through or is it all one unaltered emplacement?
Dud
?
Here are a couple of examples of how messy these minerals can be. The zircon from the Coats is a variety called cyrtolite. If you look at the photos at the bottom of the sheet you can see how
xenotime is shot through the zircon; these minerals are chemically different but structurally the same. As the zircon crystallized, the xenotime exsolved. Next example is a very strange powdery looking thorite. The normally dark glassy thorite has been replaced
by xenotime at a late stage, hence an odd altered white thorite that is about 15% REE. Note how high Dy is in these analyses. Beam sizes varied from 3 to 20 microns. Late stage xenotime alteration of minerals is very common in the district, and these types
of alteration and exsolution examples are common in many rare mineral districts.
Geo,
I would venture to say precise quantitative analysis is beyond the reach of the professionals as well. For a simple matrix it works fine but for a complicated matrix like rocks
and junk it doesn¡¯t and varies wildly.? A ?SEM Micro probe properly calibrated is great, but a wide beam on a target leaves a lot to be desired as you¡¯ll get a mix of interferences. Then there¡¯s the software, some good, some bad and none doing everything well
and all are complicated to set up.? Believe nothing, verify everything and use it as an anomaly finder, then send it out for a real ICP/MS analysis.
Soils is FP the other is a element cal.? Soils has 3 beams with filters at 50, 40 and 10 Kv Mining uses 50 and 10 Kv beams. The new software is called Geochem and you don¡¯t need
to switch between the modes. It¡¯s expensive though.? I mostly use soils mode as I¡¯m looking for ppm anomalies.
?
A direct inter-comparison is not going to work very well unlike gamma spec where the target is the source. In the XRF world we provide the source which is going to be very different
between everyone¡¯s setup, beam size, ?intensity and to a lesser extent detector characteristics.
?
I¡¯m still looking for a CdTe rig . I have a 60kV microfocus system I¡¯d like to get running with it. I can use the LE ?HPGe detectors but a CdTe will have better resolution and
no LN2 issues
Dud
?
?
"Based on the reported percentages the assay you are looking at was done using the Soils mode which is used
when looking at PPM level concentrations. The Soils mode will well over report percent level concentrations? For samples with percent grade material they would be shot with the Mining Plus mode."
I agree that precise quantitative analysis is beyond the reach of our amateur efforts at the moment. My first question is what is the difference between SOILS mode and Mining Mode? Or perhaps I
should ask WHERE is the difference? Is it a scanning technique or is it all in software?
The price of FP software has declined by about 50% already, but that took some years to happen. Meantime I think we can all agree that direct comparison to a known assayed mineral is a legitimate
goal, as long as the sensors are the same type?
That's how I do uranium ore %, Cs-137 in soil,? and radium sample estimate , by direct comparison with calibrated samples.
On another thread, has anyone else anywhere else reported getting one of these DP-5 processors up and running? It seems that maybe 20 or so of them have actually been sold, maybe a few more.
So qualitatively the results from both XRFs seem to be similar.? I will be looking at other specimens that you analyzed as well to see if they jive with my setup.
So what about the
FeSi escape vs TiKa1 issue?? Attached is a closeup of that region for the TMG columbite (was samarskite Tub #2).? It sure seems like the
TiKa1 lines up better and it would be consistent with the Ti that you detected.
On Sat, Jan 18, 2020 at 10:27 AM Dude <dfemer@...> wrote:
Charles,
Based on the reported percentages the assay you are looking at was
done using the Soils mode which is used when looking at PPM level concentrations.
The Soils mode will well over report percent level concentrations? For samples
with percent grade material they would be shot with the Mining Plus mode.? See
if we shot that sample with both modes and use the Mining Plus mode to try a
cross calibrate with.? It¡¯s doubtful that you¡¯ll get a very good cross cal as its
dependent on the element , matrix effects and detector efficiency over energy
as well as detector / x-ray geometry and x-ray flux.?
Cals are done using the Fundamental Parameter approach or by
running each element using a calibration curve.? A cal curve can be built using
an element oxide and blending it down to PPM levels. That curve is still
dependent on distance of the target to the detector / X-ray geometry (also air
temp and moisture content and air density if you want to get picky) but most
importantly is the x-ray flux and beam filtering.? For your case you would have
to normalize it to the Am-241 signal.? The system needs to have a fixed ROI for
each element and you would use the baseline corrected area in that ROI as the
measured parameter. Complicating that are matrix effects where any other peaks that
are intruding in that ROI must be de-convolved from it and the area corrected
for it. A Gaussian correction could be used The most important thing you need
to do is get a handle on the detector/X-ray/ target geometry. It must be the
same all the time. The beam angle to the target and the detector should be
changed from your dual illumination set up to a single beam path and keep the
angle around 30 deg or so to minimize backscatter.
Quantitative gamma ray spectroscopy is much simpler compared to
quantitative XRF and I never trust my XRF reported values without a great deal
of skepticism and review
Dud
?
?
?
Nearly 2 years ago (5/23/18) Dud was kind enough to shoot
some of my specimens with his XRF "gun", which has a pinpoint xray
source.? Several of my rocks were found in the rubble piles of the local
rock shop "Tucson Mineral and Gem World", which has been open for
about 60 years.? One piece is large and ugly:
Looking at my results (blue scan) the Nb peak is off the
charts!? Even more significant is that Dud's results show the same thing:
Comparing these percentages to the relative heights of the
same peaks on my scan one finds similar proportions.? It is very
satisfying to know that my results largely corroborate those of Dud's.
Also plotted is a samarskite from Little Patsy.? It has
a relatively high Y component.
?
?
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