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GeneralPoll - any micromounters using optical ID techniques / PLM?

4th Oct 2019 21:50 UTCMathieu Butler

Hi, are there any micromounters out there that are actually using optical ID techniques / PLM, RI, spindle stage, with grains (not thin sections) ,etc I assume it's a dying art since all the micromounter old-time masters who would use them for tough IDs (like Mt. St. Hilaire,etc) I know of (in New England anyway) have passed away and no one is taking it up as far as I can tell (except me) We do have some members in my club (Micromounters of New England) who took those courses for their geology major, but don't actually use them since my club has access to EDS and even one member owns a handheld raman spectrometer - the kind intended for drug detection,etc. However, optical techniques can still be usefull, we had a member trying to distinguish anthopyllite vs cummingtonite - which are dimorphs so EDS did not help, so I used extinction angle to help settle it - although my friend later confirmed it by paying for XRD

4th Oct 2019 22:38 UTCRalph Bottrill Manager

I do, but mostly for work!

5th Oct 2019 13:43 UTCMathieu Butler

Hi Ralph,  could you give me some examples of how you use the PLM for your work? 

5th Oct 2019 21:53 UTCRalph Bottrill Manager

I mostly use PLM (reflected and transmitted) on thin and polished sections to identify and characterise rocks, ores, sediments etc., sometimes going on to SEM and probe for confirmation of some minerals. With unconsolidated samples like sands, mineral concentrates and dusts I will often mount grains ( hand picked or bulk) in epoxy resins for PLM and SEM study but if in a hurry for a quick look will put a little material in RI oils on a slide with a coverslip. Most commonly I do the latter for asbestos investigations, but also forensic studies where we typically have very small samples. On occasion I will pick out mineral grains from a rock to check optical properties, though am more inclined nowadays to go to SEM if I can wait, and haven’t blown my budget. The optical properties you can easily test are RI, colour and pleochroism, extinction angle, length fast/slow; birefringence is harder, depending on grain size and getting interference figures can be very difficult. It’s a dying art but still quick, cheap and easy.

4th Oct 2019 23:55 UTCFrank K. Mazdab Manager

I do as well, although I'm not a micromounter.  Admittedly I probably spend 99% of my microscope time looking at thin sections, but I do also occasionally look at crushed grain mounts in R.I. oils, and also at larger chunks of transparent materials (mostly just for fun or for teaching purposes), for example to demonstrate pleochroism using a homemade optical instruments like a calcite-rhomb dichroscope, or to demonstrate birefringence looking at a mineral between two sheets of polarizing film.

5th Oct 2019 13:45 UTCMathieu Butler

Hi Frank,  thanks for responding, I know you said you used to teach optical mineralogy : ) 

5th Oct 2019 00:54 UTCPaul Brandes Manager

As do I. I use them at the college I teach at to show students what can be done to ID rocks, as well as to have a little fun with the "old style" techniques........ which reminds me, I need to have some more thin sections made.

5th Oct 2019 16:52 UTCDonald B Peck Expert

I use optical when I don't recognize a mineral.  Mostly, just a quick IR determination, or an extinction angle.  Rarely, I mount the spindle stage.

6th Oct 2019 00:23 UTCAdolf Cortel

I also use a polarizing microcope as a tool to confirm the identifications made with spectroscopic techniques and, very often, only for the sake of learning. I like very much using it but I spend much more time than using spectroscopic methods; furthermore, I have found that it is of little use for RI above 1.74 which is the highest RI of the liquids I have. Despite I need much more practice, in some cases the optical properties have been the clue for an identification. 
I bought (ebay) a  russian polarizing microscope LOMO POLAM lacking some pieces; I had to buy them and work a lot on adjusting everything but now it works fine. 

6th Oct 2019 01:41 UTCBart Cannon Expert

Here is a bargain ore microsocope.  $347 from India.   I have one.  It works.  It has a bertrand lens.

I think the company is named Radical Scientific Equipments Pvt.Led.   They are in Ambala Cantt, India.  I can't find their web link in the brochures.

6th Oct 2019 11:40 UTCKeith Compton Manager

Bart Cannon Expert  ✉️

Radical Scientific Equipments Pvt.Led. 
WHat model is that?

7th Oct 2019 00:51 UTCBart Cannon Expert

It is model ROM-11   "Led" should have been typed LTD.

6th Oct 2019 12:20 UTCDavid Von Bargen Manager

Looks like this with a few extra bits & pieces. 

7th Oct 2019 11:27 UTCBart Cannon Expert

The ROM-11 is the first scope shown in that link.  I've been trying to find an inexpensive ore microscope for the people in my Ore Microscopy Facebook group.   I've been frustrated for years that people will spend large sums of money for specimens, but are not willing to spend a few hundred for a decent petrographic / ore microscope.

I'm now working on a universal vertical illuminator so the a polished section can be observed effectively.  I'm planning on telling people how to make one using a microscope cover slip as the beam splitter.  Should be under $100 from me if they aren't inclined to make one.
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