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 Post subject: Re: Use of polariscope in Gem ID course?
PostPosted: Sat Oct 06, 2018 9:44 pm 
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I can second this. Pretty_temptation is a good seller. Responds quickly to questions too.


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 Post subject: Re: Use of polariscope in Gem ID course?
PostPosted: Fri Mar 15, 2019 9:47 am 
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I actually ordered my student package right at the time when they disappeared from the online store. I can't remember who I spoke to regarding them being pulled but the reasoning was the GIA polariscope was causing an electrical shock to a select few users requiring the college to come up with a new alternative.
a polariscope is still required to complete the course, they just have to be sourced elsewhere.

1bwana1 wrote:
Easier to buy a good Chinese polariscope on Amazon. They are so cheap. I have one of these, and it works perfectly. The seller is reliable as well.

https://www.ebay.com/itm/Gem-Table-Top- ... SwhcJWIL4x


it really is hit or miss then.
functional polarizing filters are what is really important but I was a little disappointed by my Chinese polariscope as the utility light does a great job lighting the stage but is too misaligned and dim to be useful for pairing up with a refractometer for a spot reading.


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 Post subject: Re: Use of polariscope in Gem ID course?
PostPosted: Fri Mar 15, 2019 1:26 pm 
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D-Flawless wrote:

it really is hit or miss then.
functional polarizing filters are what is really important but I was a little disappointed by my Chinese polariscope as the utility light does a great job lighting the stage but is too misaligned and dim to be useful for pairing up with a refractometer for a spot reading.


Agreed, the chinese polariscope lights are not very good for use with the GIA refractometer. However, the GIA polariscope also is not as good as a dedicate GIA utility light with both white and monochromatic light sources. This is the only way I use my refractometer.


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 Post subject: Re: Use of polariscope in Gem ID course?
PostPosted: Sun Mar 17, 2019 9:48 pm 
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1bwana1 wrote:
D-Flawless wrote:

it really is hit or miss then.
functional polarizing filters are what is really important but I was a little disappointed by my Chinese polariscope as the utility light does a great job lighting the stage but is too misaligned and dim to be useful for pairing up with a refractometer for a spot reading.


Agreed, the chinese polariscope lights are not very good for use with the GIA refractometer. However, the GIA polariscope also is not as good as a dedicate GIA utility light with both white and monochromatic light sources. This is the only way I use my refractometer.

unfortunately the GIA utility light isn't available for purchase. the student package now includes a monochromatic light source that gets the job done but pales in comparison to the ones they have for use in their lab and I assume is the one you're using.


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 Post subject: Re: Use of polariscope in Gem ID course?
PostPosted: Sun Mar 17, 2019 11:35 pm 
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Yes, you have to watch Ebay for one. They come up with some regularity.


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 Post subject: Re: Use of polariscope in Gem ID course?
PostPosted: Mon Mar 18, 2019 11:12 am 
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D-Flawless wrote:
I actually ordered my student package right at the time when they disappeared from the online store. I can't remember who I spoke to regarding them being pulled but the reasoning was the GIA polariscope was causing an electrical shock to a select few users requiring the college to come up with a new alternative.


I'm not sure who you heard this from, but it was certainly not the case. There was unfortunately a backorder of polariscopes which lasted around 2 months last Summer iirc. When this occurs, the item is taken off the website and instructors will provide guidance for suitable alternatives.

Although GIA has recently produced a newer version of the polariscope which is currently offered on the website, this was not due to safety issues and the old versions are still used interchangeably.

The new versions are still designed only for "white light source" use on the refractometer. A separate monochromatic light is required as well.

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 Post subject: Re: Use of polariscope in Gem ID course?
PostPosted: Mon Mar 18, 2019 11:52 am 
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A separate monochromatic light is required as well.

Or a filter.
All refractometers made by Wildman, Kruss and Eickhorst come with monochromatic filters.
I find them far superior to the ones made by GIA (sorry). I own all 3. My GIA refractometer was given away years ago.

http://www.gemproducts.com/refractometer.html


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 Post subject: Re: Use of polariscope in Gem ID course?
PostPosted: Mon Mar 18, 2019 2:21 pm 
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The main reason to have a light source other than the GIA polariscope is having a monochromatic source. It seem to me that this could be solved with a filter that can be placed between the polariscope and the refractometer.

Anyone know of a source for a good glass covered monochromatic filter?

I would think that in these days 3D printers we could come up with a good, inexpensive add on solution.


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 Post subject: Re: Use of polariscope in Gem ID course?
PostPosted: Mon Mar 18, 2019 5:19 pm 
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I've purchased one from Jeff Wildman @ GemProducts in the past. Don't know if he still sells them/\.

http://www.gemproducts.com/


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 Post subject: Re: Use of polariscope in Gem ID course?
PostPosted: Mon Mar 18, 2019 5:34 pm 
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Yes, he still sells them for $60.00. I was hoping to find a source for bulk filter material so we could make something affordable and cool.

Anyone know the specifications or the right filter or a supplier?


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 Post subject: Re: Use of polariscope in Gem ID course?
PostPosted: Wed Mar 20, 2019 5:51 pm 
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The filters are simple linear polarizing filters, still available for old camera lenses. They are different than the circular polarized filters for digital cameras.

I found them for super cheap on ebay a few years ago - we're talking in the $2/ea range for about 50mm diameter glass filters. I'm not sure if they're still that price but expect them to be available from Chinese and Indian suppliers.

Good luck!

-Allan

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 Post subject: Re: Use of polariscope in Gem ID course?
PostPosted: Wed Mar 20, 2019 6:34 pm 
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Sodium light is considered monochromatic even though it actually has two wavelengths, 589nm and 589.6nm.


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 Post subject: Re: Use of polariscope in Gem ID course?
PostPosted: Wed Mar 20, 2019 7:45 pm 
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gembug wrote:
The filters are simple linear polarizing filters, still available for old camera lenses. They are different than the circular polarized filters for digital cameras.

This is true, though circular polarizers for cameras have two stacked polarizers, a linear polarizer (which the light enters through, removing glare and such) followed by a quarter wave plate which takes the linearly polarized light and changes it over to circular polarization (apparently to avoid problems with internal reflections off flat surfaces?). If you flip the filter so light instead enters through the quarter wave plate and exits through the linear polarizer it just works as a linear polarizer, though I am not sure if the quarter wave plate causes dimming or other subtle issues.
Note that the gemmo aid microscope accessory ships with circular polarizers, so you have to be very careful with their orientation to get correct results.

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 Post subject: Re: Use of polariscope in Gem ID course?
PostPosted: Wed Mar 20, 2019 7:51 pm 
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The filters I would like to source are the sodium monochromatic filters, not the polarizing filters.


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 Post subject: Re: Use of polariscope in Gem ID course?
PostPosted: Wed Mar 20, 2019 8:07 pm 
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Quote:
I would like to source are the sodium monochromatic filters

Ah, sorry, my misunderstanding!

My friend eBay once again has them - 590nm optical bandpass filters. Close enough to sodium for all intents and purposes. I bought them to filter yellow LEDs for my refractometer, then found LEDs that are 590nm (sold for car indicator lights).

https://www.ebay.com/itm/2pcs-Optical-Filter-590nm-narrow-band-pass-filter-8-0x8-0mm/262750817435

I can't find the link for the LEDs modules I ended up with, sorry. If I find the link I'll post it.

Stephen - interesting to know about flipping the circular polarizing filters over to use as linear. I learned something new!

-Allan

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