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Techniques for CollectorsWhich ID technique is best?
13th Apr 2016 11:33 BSTJoshua Chambers
As a beginner, I often wonder which ID technique is best and how to know what ID technique would be best for a certain situation? All ID techniques differ, but why are some preferred in certain situations to others? For example, why would EDS be better than XRD in one situation and XRD be better than EDS in another? How do some of these techniques differ and what do they entail?
Also apart from EDS/WDS, XRD, RAMAN and probing(?) are there any other ID techniques that are useful to know about?
If you had a polymorph (same chemistry different crystallography) you would not be able to tell them apart by EDS. If you had a mineral that was amorphous, you wouldn't be able to use XRD. You also need to be able to get a large enough pure sample to do XRD. Also not all elements are able to be detected with EDS (the lighter ones)
13th Apr 2016 14:50 BSTDavid Von Bargen Manager
Also, cost of EDS is about one fourth of that of XRD. I can't afford XRD except for rare occasions, but I can send out a few grains for EDS every month if I want.
13th Apr 2016 15:03 BSTKyle Beucke
Some real-life examples of benefits of each: I have a black, massive sulfide samples that on EDS analysis were determined to be copper-arsenic-antimony-sulfide (that is all EDS can do). Could be enargite, tennantite, etc. XRD determined one sample to be luzonite, and another to be a mix of famamtinite and luzonite (EDS would not be able to do this).
A few tiny, sub-millimeter grains of what I think is gold in quartz. Grains are too tiny to use XRD, but EDS was able to identify the material as gold because it focuses the beam on a very tiny spot.
Josh, another powerful technique that you can learn to do yourself is optical analysis of transparent minerals using the spindle stage. It requires a polarizing or petrographic microscope. The spindle stage can be purchased or home made. The resulting data include the refractive indices, biaxial or uniaxial, and 2V (the angle between the optic axes of biaxial minerals).
13th Apr 2016 16:22 BSTD. Peck
Thank you for the replies guys! Very helpful!
13th Apr 2016 16:59 BSTJoshua Chambers
In reply to Don, can you turn, say a cheap biological microscope into a polarising microscope using a polarising filter, or is it more complicated than that? (I am only a beginner :-D) That is a useful tool to have and will definitely look into that in the future. Can you use polarising microscopes for much else, and if so, what?
Yes, a biological scope can be modified to be a polarizing scope. I did it and that is what I use. It requires a polarizing filter below and another above the stage. A crosshair reticle in the ocular and a set screw so the ocular cannot turn. A circular stage calibrated in 360o mounted so it can turn (mine is on a lazy susan bearing). And a way to center the stage in the train of optics. The analyzer (the upper polarizer) should be able to slide in and out of the optical path. Mine lacks a Barlow lens, which makes observing optic figures difficult, but it can do most other things.
14th Apr 2016 02:35 BSTD. Peck
I lengthened the optical path by inserting body between the ocular and the main body of the scope. It accomodates a slide that carries the analyzer and a second slide that carries wave plates.
Centering the stage is important. If you cannot do it, the grain/crystal will constantly move in and out of your field of view as you turn the stage.
I can mount the spindle stage, observe cleavages, observe the type of extinction and measure it when inclined, observe whether the crystal is length fast or length slow, measure refractive indices.
Modifying the scope is not easy. You need to like to tinker, be a bit inventive, and have some patience. My first one was a child's toy. It had the polarizer cemented below the stage, the analyzer on a pill vial drilled and dropped over the ocular, and a cardboard stage with a tube cemented at the center and inserted in the round hole in the stage. It was crude, but effective.
You did not mention that you need thin sections for petrographic microscopes!
14th Apr 2016 07:38 BSTVolkmar Stingl
What to say about RAMAN pros & cons?
14th Apr 2016 08:34 BSTLuca Baralis Expert
It should be cheap, but less easy to access, I think.
Wow, thank you for all the informative answers. I have had all my questions answered.
14th Apr 2016 08:50 BSTJoshua Chambers
Don, I have a cheap old stereo microscope with only 20x magnification (I could buy more powerful eyepiece lenses), could that be turned into a polarisng microscope using the same principles. The stage doesn't move, so that could be an issue right? What kind of magnification do you need?
A DIY rotating stage
14th Apr 2016 11:35 BSTDavid Von Bargen Manager
14th Apr 2016 13:50 BSTHolger Klapproth
another method that I really like is infrared spectroscopy (FTIR). This is different from raman and you need a reference spectrum to know what you have. Very powerful for some of the minerals you find fumaroles for example. Normal FTIR does not work on sulfides (you need extended spectrum devices that are very very rare go that). But since Nikita Chukanov has published thousands of reference spectra in his book this is a really helpful technology especially when minerals have ammonia for the volatile material content - even if we have to exclude the sulfides.
For those interested:
Infrared spectra of mineral species: Extended library (Springer Geochemistry/Mineralogy) 2013 ISBN-10: 9400771274
Bought the book and I really like it. But I have access to a FTIR.
Volkmar, I agree that thin sections are necessary for rock, but you don't need them for minerals. The spindle stage is designed either for tiny crystals or for grains. The grain size is not terribly important. If you are interested, I recommend The Spindle Stage, Principles and Practice by Donald Bloss, Cambridg University Press, 1981. ISBN 0 471 31266 5. The spindle stage itself is extremely simple and easy to make. It is quite forgiving of small errors and in fact when this topic is taught in university classrooms, the students often make their spindle stages from cardboard. A quick overview can be obtained from the McCrone Spindle Stage Short Course. . .; Microscope, Vol 52:1 pp 23-39, 1981.
14th Apr 2016 16:59 BSTD. Peck
Josh, If that stereo scope that you have is the type we usually use for looking at minerals, it won't work. You need the type that is used in high school biology labs. If you can get one, the American Optical AO60 with a microglide stage (under $100 used) is the easiest to adapt. The microglide stage takes care of the centering problem.
The spindle stage consists of a small protractor, about 1.5 cm radius, with a detent notch every 10o. A short length of hypodermic tubing is bent to form a radius with a right angle bend on one side to fit into the detent notches and a right angle bend on the other that extends through the "origen" hole through the protractor. The protractor is fixed to a base that is notched to hold a microscope slide. The base is fastened to the microscope stage.
In use a mineral grain (pinhead sized) is stuck to a needle point with nail polish and the needle inserted in the tube and centered in the optical path. Mounting an acceptable grain is the most difficult part of the operation. The position is tested. Then with the radius and stage are turned to extinction. This is repeated with the radius incrementally increase 10o each time. The data can be resolved using a Wulff net or (much easier) using EXCALIBR, a program developed by Don Bloss, Bob Downs, and others (freeware). It returns among other things: 2V for biaxial minerals, the radius and stage settings for the refractive indices for transparent minerals (of course not isometric). Then the stage and radius are set and the a small oil cell inserted in the spindlestage base to measure the refractive index.
It all takes about 20 or 30 minutes, once a good mount is obtained.
Thank you, Don, for the interesting informations!
14th Apr 2016 17:05 BSTVolkmar Stingl
Volkmar, I have been collecting micro crystals for about 60 years. When I first started I wondered how one ever tells them apart for id work. Since I was a chemistry teacher I started using semimicro qualitative analysis. Later learned crystallography and then tried optical. I get a lot of satisfaction from doing my own analysis. Curt Segeler (segelerite) introduced me to the spindle stage. I am convinced that it is the most powerful id tool available to the amateur (short of paying for EDS or XRD, etc) Curt also introduced me to another very useful device, the ring furnace, for microchemical analysis.
14th Apr 2016 17:34 BSTD. Peck
Thank you Don for so much information and knowledge. I am definitely looking forward to making my own spindle stage and polarisng microscope.
14th Apr 2016 18:19 BSTJoshua Chambers
What magnifications are best at viewing the micro crystals?
And will any polarising filter work, like a camera one? Also, I see polarising filters for £100 ($140) and some others for £10 ($14). Is there much difference, or is it brand name?
Luca Baralis Wrote:
14th Apr 2016 19:40 BSTGünter Frenz Expert
> What to say about RAMAN pros & cons?
> It should be cheap, but less easy to access, I
With Raman-spectroscopy you see differences in crystal structure. Not as accurate as XRD but same direction. As an example take a look at Smithite and Trechmannite, both are red sulfosalts with exactly the same chemistry but different crystal structure. With EDS you have no chance, with Raman and XRD you can tell them apart. When you are careful with your Raman-system you don't even damage the crystals. On the other hand you have no chance to tell apart if your Chabasit is Ca- or Na-dominant with Raman, this would be a job for EDS.
15th Apr 2016 03:22 BSTD. Peck
I have a 10x ocular and 5x, 10x, 40x objectives. I never use the 40x and seldom use the 10x. As to polarizing filters, I don't know whether photo types will work, although I can not imagine that they wouldn't. But you want plastic that you can cut to size. Edmund Scientific (I think in Tonawanda, NY) sells different grades. They also sell an experimenter's kit that includes a couple of different grades, plus sheets (3" x3") of 1/4 wave retardant material. It is a good buy, and use the lighter colored polarizing material. Darker color will work, but it affects the colors you see. For that matter, the lenses from old polaroid sunglass will work (bat they are darker colored as well).
David, I just looked at the rotating stage in the links you offered. It looks good and is a bit thinner than mine. I used a plastic naval bearing-averager mounted on a lazy susan bearing that mounts on my stage. I works, but the lazy susan bearing has a little slop in it - not much, but enough to be annoying. The design in the link looks like it might be tighter. Thanks.
15th Apr 2016 11:23 BSTJoshua Chambers
So the lighter the filter the better? or does it just depend on what you're looking at?
Also, I've found different types of polarising filters: circular, linear, calcite etc. Which type should I be investing in?
I've looked on the Edmund scientific website and cannot find the experimenters kit you are talking about. Could you possibly send me a link?
I believe Edmund Scientific was sold off (I think they were bought by Wards eventually)
15th Apr 2016 13:22 BSTDavid Von Bargen Manager
Ward's kit for polarizing accessory to microscope
Josh, you want the linear type, which is the common one.
15th Apr 2016 17:31 BSTD. Peck
David, Yes, Wards bought Edmund several years ago. For some time, they maintained the Edmunds line of products, but I just checked and they no longer do so. In fact, their line is a bit thin.
I just checked Fisher Scientific and they have a good line.
Catalog No. S95559 seems like it would be good at about $20.
Thank you so much Don. You have been a lot of help and taught me a lot.
15th Apr 2016 18:25 BSTJoshua Chambers
When I begin building this I may private message you if I need help.
Your help is greatly appreciated!
If you are interested in home IDing of minerals, you should really get Don's book on the subject (I highly recommend it)
15th Apr 2016 22:29 BSTDavid Von Bargen Manager
Thank you, David. And there is a complete discussion in an appendix of how to alter a student grade biological compound microscope to a polarizing scope (or at least one way to do it).
16th Apr 2016 01:49 BSTD. Peck
Hi Mr. Peck,
24th Jan 2017 22:42 GMTMathieu Butler
Thanks to your posts , I am very interested in the PLM and spindle stage and have been trying to read everything I can find online and have ordered the Optical Crystallography book by Bloss (replaces An Introduction to the methods of Optical Crystallography (1961) and The Spindle Stage: Principles and Practice (1981))
Very exciting that an amateur can do this type of analysis at home for less then a fortune, thanks for getting this information out there.
Could you give me a brief description of the steps you take so I have some idea of what I would need to purchase? (besides a PLM or home made version)
Would I need to buy the whole range of RI fluids or is there a shortcut?
From my understanding now, you need to:
mount the xl (in RI fluid cell or air ?)
take extinction readings at different stage / spindle settings
enter that data into excalibr to get optical indexes
use stage/spindle settings that excalibr outputs to test RIs
25th Jan 2017 02:29 GMTDonald B Peck Expert
Thank you for your interest. Where to start.
You need a petrographic (student grade is fine) or polarizing microscope, which you can build. The stage must be graduated in degrees, rotatable, and centerable (or have centerable optics). And the analyzer must be removable: in/out. The spindle stage can be home made. University students make their own out of poster-board; mine is lucite. It is very forgiving of small errors. You need an oil cell (more later). And you need oils. A full set with 0.05 intervals is nice, but a bit expensive. Common oils (cinnamon, clove, rapeseed, etc) can be used. Especially if you can live with estimates between two oils, used as fences. I did buy bromoform and methylene iodine to get something in the higher ranges.
If your budget will stand it, buy a student grade petrographic. Make the spindle stage. The oil cell is made by cementing two short lengths of large paperclip wire onto a microscope slide with epoxy and then a small piece of cover slip on top of them. The cell should be about 4 ro 5 mm square, otherwise you will think you are pouring your oils down a drain. Keep as small as possible but so the needle from spindle stage is centered in it.
Getting a good grain mount is the most difficult part of the process. Take about 6 needles that fit in the spindle. Using fine emery paper grind the points off at a random angle, not perpendicular to the shaft. The grain (size doesn't matter much) is stuck to the needle by dipping the needle's tip in red nail polish (so you can tell the grain from the cement) and then touching it to the grain. If you use the normal point of the mineral, the drying cement tends to pull and flat sided crystal or cleavage face to a perpendicular position, and this usually means you are looking down an axis -- not good.
I would suggest that whenever you are going to use the spindle stage, make up six or so grain mounts so that if one doesn't work, you can try another. In the long run this saves a lot of time and aggravation.
Then comes the testing for position and taking the data. Don Bloss'es book is a great reference, albeit a little deep. Pay attention to the captions under the illustrations. I learned a lot from them. I hope you can use EXCALIBR-W. So far I have had no luck running it on Windows 10. Finding the solution on a Wulff net is a bit more work. McCrone's "Microscope" Vol 52:1 has a great article on How To, and another on the comparison of student made spindle stages, to research grade scopes and spindles. Turns out the student spindles were pretty good.
This has been long . . .I hope it helps.
Under a scope i used oils and liquids to check out the R.I of crushed grains of an unknown massive mineral found in quartz vein. After checking the grains in polarization normal light we tested with some liquids to determine the R.I
25th Jan 2017 05:41 GMTMatt Neuzil Expert
Its been 10 years since i did this with aid of my professors help so its a bit fuzzy the exact details how that all happened.
We did find that the unknown was apophyllite.
I am not sure how useful that is, but since were talking scopes and rotating stages i thought it a little related.
In regard to the original question, before contemplating an analysis, one should first exhaust the basic "visual" techniques for mineral ID - color, luster, hardness, streak, fluorescence, crystal forms, etc., because these will narrow down the possibilities to the point where you can determine which analytical technique is necessary. Both chemistry and structure are needed to ID a species, but usually one of these is evident from the "visual" ID or from field information such as the geoenvironment it was found in, so usually one only needs to analytically determine either the chemistry or the structure, rarely both. For example, a visual assessment and field information may determine that your unknown is a garnet. So you know the structure, it's just a matter of learning the chemistry to determine the species, and so EDS or XRF (metal content) will be enough. Conversely, based on visual and field info, a yellow powdery mineral could be greenockite or hawleyite, both are chemically CdS, so XRD is needed in this case.
25th Jan 2017 14:44 GMTHarold Moritz Expert
Even though EDS cannot detect the light elements H, He, Li and Be, it can still be very useful if the visual and field information are applied. I recently had EDS tested a glassy unknown found in a pegmatite. It was purported to be phenakite - there was no crystal form so that info was missing. EDS detected only O, Si and Al. The presence of Al rules out phenakite. As to what it really is, clearly a light metal was not detected, in this case Be or Li, but of the 5 possible minerals only beryl matches the mineral's visual properties and occurs in that geoenvironment.
Raman spectroscopy works in a totally different way and can uniquely ID a substance by its unique structural vibrations induced by a laser, which vary with the chemistry as well. Also non-destructive and only a small amount needed. But it does not work with all minerals as many will fluoresce or give false results. But if one has easy access to it, then give it a go.
"Even though EDS cannot detect the light elements H, He, Li and Be " Actually the newer machines can detect Li and Be. see: https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S1431927613007678
25th Jan 2017 15:27 GMTReiner Mielke Expert
That's great! Though obviously not every place has the latest machines. So, inquire first.
25th Jan 2017 17:51 GMTHarold Moritz Expert
Don, that is intensely analogue and very old school and I am impressed that you routinely do such work! But an observation......if you did this as a service for others, you'd have to charge much more than EDS for sure, because of the time involved. RI oils are expensive and frequently toxic.
25th Jan 2017 19:15 GMTTony Peterson Expert
So lazy people like me will continue to use microanalysis :)
Hi Mr. Peck,
25th Jan 2017 21:10 GMTMathieu Butler
Thanks for your detailed reply.
I saw the previous post where you mentioned your book (Mineral Identification: A Practical Guide for the Amateur Mineralogist) has a section on how to alter a student grade biological compound microscope to a polarizing scope.
Does your book also cover the PLM and spindle scope ID techniques and hacks / detailed steps? (so I don't have to bother you with any more questions here)
Hopefully, a "dummies guide to Optical Crystallography" written more for the micromounter?
Thanks again for your time,
Hi Tony, I have to admit that I don't use tha spindle stage very often . . . it is kind of a last resort. Setting it up, mounting the spindle, and mounting the grains is what takes time. Taking the data and processing it is no more than 10 or 20 minutes. However, I do pull the polarizing scope out a bit more often to look at small crystals, cleavage fragments, or grains as I try to sort out the ID of a mineral. There is quite a bit that can be quickly learned.
26th Jan 2017 02:18 GMTDonald B Peck Expert
Matt, I tried to cover the use of the PLM. It doesn't really matter whether it is a home adapted scope or a commercial model, the process is about the same. I devoted a chapter each to cleavage, extinction,elongation, refractive index, birefringence, etc; and at the end of each there is a "By The Numbers" how to do it. For the spindle stage, there are two sets of instructions, one for solution with a Wulff Net and the other using Excalibr. Quite honestly, there is a learning curve. I tried to keep it as low as possible.
26th Jan 2017 07:48 GMTIlkka Mikkola Expert
Modern EDS can detect litium if it is almost pure (not oxidised) metal.
See for instance: https://tools.thermofisher.com/content/sfs/brochures/WS52730-Detecting-Lithium-EDS.pdf
Apropos MicroRaman spectroscopy, below is a picture that in a very practical way tries to demonstrate the size range involved with this analytical method. Naturally, for SEM-EDS etc this is no big deal at all, that's not the point.
26th Jan 2017 11:20 GMTJoel Dyer
And I'm not commenting on what method is best for whatever: it varies & many methods are usable and even often needed together, as we know.
Too bad I don't yet have 2 x ND400 filters, then could have demonstrated the very, very small spot size, in a way. Ran out of time here, so the spectrum is not that clean either. But other work is beckoning...
One method does not fit all, it depends on the species. However generally the cheapest and most versatile is EDS. All the old fashion methods require relatively large specimens, especially if you plan on doing quantitative analysis, and are destructive.
26th Jan 2017 16:02 GMTReiner Mielke Expert
Hi Mr. Peck,
31st Jan 2017 05:12 GMTMathieu Butler
Thanks for the info and encouragement, I have your book on order and look forward to seeing what can be done at home with a PLM.
But I can't seem to find the EXCALIBR-W program anywhere online for downloading including http://www.webpages.uidaho.edu/~mgunter/programs/programs.html whose links all seem to be missing now.
Do you know where to get a copy?
It's on a CD included with Don's Book.
31st Jan 2017 11:34 GMTDavid Von Bargen Manager
31st Jan 2017 16:22 GMTDonald B Peck Expert
As David said, it is on the CD. Are you using Windows 10? If so, you may have some loading problems. In that case, contact me and I will try to help. EXCALIBR is a 32 bit program.
Hi Mr. Peck,
15th Feb 2017 02:30 GMTMathieu Butler
Got your book and am working my way through it - great stuff!
EXCALIBRW seems to run fine on my windows 10 home 64 bit OS.
Hi Mr. Peck,
15th Feb 2017 04:12 GMTMathieu Butler
Turns out I was wrong, none of the programs from the CD will install on windows 10 home 64-bit.
Trying to run any of the setup.exe's gets the error dialog "this app can't run on your pc - to find a version for your pc, check with the software publisher"
After doing some google research I found that apparently it's an old install shield setup.exe
(and right-click details on setup.exe shows : file version 18.104.22.168 / installshield)
I found a link to the "InstallShield 3 32-bit Generic Installer 3.00.117.0"
and downloaded it and copied it's setup32.exe into the "MinSearch 4.00" folder that has the old setup.exe and ran setup32.exe instead and it
works - it installed and runs fine now.
I copied the setup32.exe to the other install dirs (excalibr_w, MinIDCalc) and
EXCALIBRW now installs and runs fine.
MinIdCalc installs , but still won't run - same generic error "this app can't run on your pc - to find a version for your pc, check with the software publisher"
I'll keep working on that one...
15th Feb 2017 06:29 GMTJoel Dyer
Windows 10 has opened a bunch of Worm Cans for many of my IT customers at least. Especially thinking that many of my customers are 60-80+ years of age & not technically trained... And I ain't gonna upgrade my work laptop to WIN10 becasue of software compatibility & the many problems with WIN10.
Having got to know many quirks and issues - such as (failed) Updates screwing up WLAN and mobile connections and the whole Operating System -, I've recommended my customers to bring in their upgraded or new PC to me & I'll put it into the condition it should be in the store already and more, including installing Classic Shell. But I guess I should thank Gates & Co. for the work WIN10 brings me ;-)
You might be able to install a VIrtual Machine inside your Win10, if you have a license tag somewhere for WIN7 or something. I'm not responsible for any possible license violations or endorse them, so Microsoft don't bother hassling me, OK?
Not sure if the below video is of any help to you.
15th Feb 2017 20:21 GMTDonald B Peck Expert
That is great news! The old Install Shield was 16 bit and wouldn't run. I thought the only solution was going to be for me to buy a new version of Install Shield and rebuild the disk. And a new version was simply two expensive. And thanks for the link. I am glad your problem is solved. I'll work on the MinIDCalc problem, too.
15th Feb 2017 23:58 GMTMathieu Butler
Joel, thanks for the VM suggestion, I had seen that option in my searches but managed to get installshield to work with the install shield generic 32 bit download.
Don - glad I could help. It would be a great shame if these programs were lost to time, I wonder if mindat would consider hosting them? (assuming the authors do not mind)
Matt that is a good thought.
16th Feb 2017 00:48 GMTDonald B Peck Expert
1st Jun 2018 10:22 BSTFlorian D.
As some people seem to use the spindle stage, I thought this forum would be apt to announce that I have written a new (and free!) program to obtain optical parameters like 2V and the direction of axes from spindle stage measurements. The program, called "GrimR", actually is a package which can be loaded in the free statistics package "R". I choose "R" on one hand, because I work as a statistician and it offers me many tools to do error propagation and graphical visualization. On the other hand, it is system independent.
"R" can be obtained here: https://www.r-project.org/
And GrimR can be load from the "Comprehensive R Archive Network" (CRAN) or one of its multiple mirrors from inside R.
The idea to write my own program grew when I was taking some mineralogy class 2 years ago. Afterwards I was reading some articles and came about a description of the spindle stage. I wanted to understand better how one obtains the optical parameters from these measurements and found the original articles from the 1950's very cumbersome. I found a way to derive the relevant equations more directly, which I documented here: https://arxiv.org/abs/1703.00070
Specifically, I was not content with the estimation procedure used in Excalibr and thought that my method will give more reliable error estimates.
In practice, the results form GrimR and Excalibr coincide quite well, but GrimR is often still able to cough up a solution when Excalibr fails to do so.
I would like to thank Prof. Mickey Gunter and his PhD student Steven Cody who provided me with a version of Excalibr and also some Excel sheets Steven wrote.
In the meantime Excalibr and these sheets became available from the Minsocam Homepage: http://www.minsocam.org/msa/Monographs/
Since nobody has mentioned it, LIBS (laser induced breakdown spectroscopy) is a useful technique for the low atomic number elements (H, Li, Be, B) and the most of metals. It is a sort of atomic emission spectroscopy where a pulse of a laser vaporizes and excites the sample. In its simplest form it is not quantitative and some important elements are hard to detect (S, C) but despite of this it is very useful to determine which elements are present in a sample. The figures show the analysis of alkaline metals in some micas (the aim here was detecting which ones contain rubidium) and in a tourmaline (elbaite)
3rd Jun 2018 20:45 BSTAdolf Cortel
Florian - Thanks for posting, I'll definitely check it out
3rd Jun 2018 21:19 BSTMathieu Butler
Hi Don - I have sent you a PM. Regards, Steve
20th Jul 2018 12:55 BSTSteve Sorrell Expert
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