October 9-10; LOS ALTOS, CALIFORNIA: Annual show; Peninsula Gem and Geology Society; Los Altos Community Center, Sat. 10-5, Sun. 10-5; free admission
Welcome to the GemologyOnline.com Forum
A non-profit Forum for the exchange of gemological ideas
It is currently Sat Sep 25, 2021 11:36 am

All times are UTC - 4 hours




Post new topic Reply to topic  [ 20 posts ]  Go to page 1, 2  Next
Author Message
 Post subject: Presidium Duo Tester II
PostPosted: Sat Sep 11, 2021 11:56 pm 
Offline
Established Member

Joined: Sat Sep 11, 2021 9:38 pm
Posts: 15
Location: Oxford NC
Hi,
I'm brand new to this website. I've collected rocks all my life and I'm 71. Just in the last few years I have started to take more interest in Gemstones. That said, I just purchased a Presidium Duo Tester II to help me verify the cut gems I own. I used it just this evening for maybe 2 hours. I hope someone here might be familiar with that model? This model is supposed to permit one to complete a Thermal test and a Reflective index test.
The Thermal Conductivity tests seem to be pretty accurate in identifying the stones I have tested so far.
The more than a half dozen blue Sapphires I tested all fall into the Sapphire range. A so called Ruby I bought that was very inexpensive from China appears to not be a Ruby, most likely a Garnet and the thermal test pointed that direction as well. Also 2 emeralds I bought from the same seller don't appear to be actual emeralds but they aren't glass either, as they look more like Tsavorite garnets and fall into the Garnet range but they are cut well and very attractive so I don't mind.
The problem I'm having is that the Sapphires don't match the numbers they should when I do the reflective index tests. Neither do the other stones I have tried. All the numbers are reading low. The sapphires read in the range of Emeralds and a Emerald reads lower than it should as well. I have recalibrated it several times. I've noticed also if I switch from wall power to batteries it requires a recalibration but the numbers don't change per stone. I've watched Youtube video's as to how to properly place the stones and cover them while doing the reflective index tests. The tests give me pretty consistent numbers when using the same Sapphire but not all sapphires have the same reflective index numbers and again they are quite a bit lower than the chart numbers listed for Sapphires. Any ideas?

Thanks in advance,
Terry


Top
 Profile  
Reply with quote  
 Post subject: Re: Presidium Duo Tester II
PostPosted: Sun Sep 12, 2021 9:36 pm 
Offline
Site Admin
User avatar

Joined: Sun Oct 16, 2005 12:22 pm
Posts: 20987
Location: San Francisco
Hi Terry.
I wish you joined the forum before you purchased this Presidium gadget.
These devices are unreliable and we do not recommend them.
"Any ideas?"
Can you still return it for a refund?


Top
 Profile  
Reply with quote  
 Post subject: Re: Presidium Duo Tester II
PostPosted: Sun Sep 12, 2021 10:08 pm 
Offline
Established Member

Joined: Sat Sep 11, 2021 9:38 pm
Posts: 15
Location: Oxford NC
Barbra Voltaire, FGG wrote:
Hi Terry.
I wish you joined the forum before you purchased this Presidium gadget.
These devices are unreliable and we do not recommend them.
"Any ideas?"
Can you still return it for a refund?


Thanks Barbra,

I will check the website I bought if from (Mineral lab) and see if it can be returned. So is Presidium generally a brand that is not recommended here? What instrument would you suggest I purchase? I did find the instrument worked quite well in the thermal conductivity mode for getting one in the ballpark and easily detected Corundum gems from other gems and Diamonds fell into the proper category and garnets seemed to as well.

It was just the optical tests that were totally off.


Top
 Profile  
Reply with quote  
 Post subject: Re: Presidium Duo Tester II
PostPosted: Sun Sep 12, 2021 10:22 pm 
Offline
Gold Member

Joined: Thu May 12, 2016 2:18 am
Posts: 1301
If you are still in the window allowing a return of the Presidium then I recommend that you do so. If not, find a nice deep drawer, put it in there and never use it again. It will just lead you astray.
Get some proper Gemological instruments, learn to use them.. It is more accurate, and fun to learn the science behind gem ID.

Welcome to the site!


Top
 Profile  
Reply with quote  
 Post subject: Re: Presidium Duo Tester II
PostPosted: Mon Sep 13, 2021 6:37 pm 
Offline
Established Member

Joined: Sat Sep 11, 2021 9:38 pm
Posts: 15
Location: Oxford NC
1bwana1 wrote:
If you are still in the window allowing a return of the Presidium then I recommend that you do so. If not, find a nice deep drawer, put it in there and never use it again. It will just lead you astray.
Get some proper Gemological instruments, learn to use them.. It is more accurate, and fun to learn the science behind gem ID.

Welcome to the site!


I should be in the window I just received it this past Saturday. I actually boxed it up to get ready to ship. I will likely have to pay a restocking fee. I hate to ship it back as it looks like the seller just has a small business so before I ship it tell me what are proper Gemological instruments?

For what it's worth I do have a nice gemstone Microscope. I have also bought used a couple used rock saws and a faceting machine. But I have zero experience using them.

Also, I have been buying cut Blue sapphires off and on from Indian via Ebay. They look nice and seem to be pretty much eye clean but they are really inexpensive. I think the most expensive one I bought is under 30 dollars. Is there a chance some of these could be heated Tanzanite or some other stone? Most are under 2 Ct. I ask because gem grade Tanzanite would sell for less and likely have much fewer inclusion's. It would also explain the lower refractive index readings I was seeing using the meter I bought. I initially was just buying a few uncut raw gemstones but lately I started buying a few cut stones along with some Semi mounts to make a ring for my wife which turned out nice and now I'm working on one for one of my daughters. I bought a nice green 8x6 Tsovorite garnet fpr my daughters ring. It's the first stone I paid more than a 200 for. It just came in today from Thailand and is beautiful.

Thanks in advance,
Terry


Top
 Profile  
Reply with quote  
 Post subject: Re: Presidium Duo Tester II
PostPosted: Tue Sep 14, 2021 11:59 pm 
Offline
Established Member

Joined: Sat Sep 11, 2021 9:38 pm
Posts: 15
Location: Oxford NC
1bwana1 wrote:
If you are still in the window allowing a return of the Presidium then I recommend that you do so. If not, find a nice deep drawer, put it in there and never use it again. It will just lead you astray.
Get some proper Gemological instruments, learn to use them.. It is more accurate, and fun to learn the science behind gem ID.

Welcome to the site!


Thanks bwana,

I was hoping someone would tell what proper Gemological Instruments I should be using but since no one has and I'm not the most patient person I started checking out the beginner sight.

So after exploring I'm assuming you good folks mean things like the Dichroscope, Spectroscope, Chelsa Filter maybe also the Refractometer? I was also looking at checking the specific gravity hydrostatic method. But the method I think I liked most that I saw somewhere in this site was using a GemmoRama-532, but working much of my life in communications I'm kind of a meter guy I guess. But since I don't have 10 grand I guess I'll have to stick to the lower priced tools of the trade.

I have one major question right now - The first thing I would like to do is to verify my blue sapphires are really sapphires (since I have more of them than anything else) and not Tanzanite or Topaz etc. What testing gear would you suggest I purchase first to test my blue sapphires? Or should I go to a different page to ask this question?

Thanks in advance
Terry


Top
 Profile  
Reply with quote  
 Post subject: Re: Presidium Duo Tester II
PostPosted: Wed Sep 15, 2021 1:28 pm 
Offline
Site Admin
User avatar

Joined: Sun Oct 16, 2005 12:22 pm
Posts: 20987
Location: San Francisco
As important as having proper instruments and tools is, more importantly is the ability to use them properly and know how to interpret the results they are giving you.

Certainly, you appreciate, thorough instructions on mastering gem identification are beyond the scope of this platform.
Barbara Smigel's site is a good place to start.
https://www.bwsmigel.info/

Our GemologyProject also supplies solid information:
https://www.gemologyproject.com/wiki/in ... _gemstones

I was trained in Germany and they have a slightly different approach (at least they did at the time) than the GIA, Their philosophy is to let your instruments identify an unknown. Don't start by looking at a stone and making assumptions as to what it might be. You might be wrong and that will sully an unbiased view of your testing results.

Establish a routine and use it to eliminate possibilities. The following videos are courtesy of Gem-A
Polariscope:
https://www.youtube.com/watch?v=4zlIA6SxZNk
Refractometer:
https://www.youtube.com/watch?v=1yRVyK5gd7s
London Dicroscope
https://www.youtube.com/watch?v=QBKKxEc8SMY
10X Loupe
https://www.youtube.com/watch?v=FwDIsvbumbo
Fluorescence
https://www.youtube.com/watch?v=1mxbxa36ppA

These should certainly get you started.

You mentioned the GemmoRaman532. Yes, definitely reliable. I rely on one daily! A wee bit more expensive than the instruments listed above: 13500€

Here are some tutorials
https://www.youtube.com/watch?v=fwk8sGBxTAk
https://www.youtube.com/watch?v=mgAy6YAPhj0
https://www.youtube.com/watch?v=zg4N_9K80Ss
https://www.youtube.com/watch?v=gVzeEhF56rk


Top
 Profile  
Reply with quote  
 Post subject: Re: Presidium Duo Tester II
PostPosted: Wed Sep 15, 2021 3:21 pm 
Offline
Gemology Online Veteran
User avatar

Joined: Tue Apr 05, 2016 7:58 pm
Posts: 914
Location: San Marcos, CA
Just speaking as a gem cutter and not a trained gemologist other than by experience and what my spouse has taught me.
Sapphires, cheap and from indian eBay sellers and now a Tsavorite from Thailand. You really need to invest in some adequate tools, and learn the basic tests. Barbra's suggestions are very appropriate.

One you stated you have a decent scope, have you learned anything about what to look for in a corundum, there already cut and polished stones and not rough so that's advantageous.

A simple but descent specific gravity test apparatus. This is my first test.

A decent polariscope/refractive index unit (we use GIA). Sometimes used units come available.

This will get you the answers to eliminate gems they are not.

Your sapphires, are very likely to be sapphires and very well might be treated like glass-filled or dyed, it may be possible you can see this in your scope. I only point this out due to your comments of readings inconsistent to each other and of course cheap.

_________________
The Gem Garden
San Marcos, CA


Top
 Profile  
Reply with quote  
 Post subject: Re: Presidium Duo Tester II
PostPosted: Wed Sep 15, 2021 3:36 pm 
Offline
Site Admin
User avatar

Joined: Sun Oct 16, 2005 12:22 pm
Posts: 20987
Location: San Francisco
Sapphires and rubies (aka corundum) as well as garnet varieties and diamonds are VERY common.
The great majority of them are ground and used as abrasives for sandpaper and drill bits.

In our line of work, one must be able to separate a gem from terrarium fodder.
May I suggest an excellent book by Richard Wise.
Secrets of the Gem Trade


Top
 Profile  
Reply with quote  
 Post subject: Re: Presidium Duo Tester II
PostPosted: Wed Sep 15, 2021 6:42 pm 
Offline
Established Member

Joined: Sat Sep 11, 2021 9:38 pm
Posts: 15
Location: Oxford NC
Barbra Voltaire, FGG wrote:
Sapphires and rubies (aka corundum) as well as garnet varieties and diamonds are VERY common.
The great majority of them are ground and used as abrasives for sandpaper and drill bits.

In our line of work, one must be able to separate a gem from terrarium fodder.
May I suggest an excellent book by Richard Wise.
Secrets of the Gem Trade


Thanks Barbara,

Per your recommendation I just ordered a copy off Ebay. They have a new revised addition out now which is great because now the older original addition can be had for cheap so I just ordered a copy.


Top
 Profile  
Reply with quote  
 Post subject: Re: Presidium Duo Tester II
PostPosted: Thu Sep 16, 2021 2:28 pm 
Offline
Established Member

Joined: Sat Sep 11, 2021 9:38 pm
Posts: 15
Location: Oxford NC
glhays wrote:
Just speaking as a gem cutter and not a trained gemologist other than by experience and what my spouse has taught me.
Sapphires, cheap and from indian eBay sellers and now a Tsavorite from Thailand. You really need to invest in some adequate tools, and learn the basic tests. Barbra's suggestions are very appropriate.

One you stated you have a decent scope, have you learned anything about what to look for in a corundum, there already cut and polished stones and not rough so that's advantageous.

A simple but descent specific gravity test apparatus. This is my first test.

A decent polariscope/refractive index unit (we use GIA). Sometimes used units come available.

This will get you the answers to eliminate gems they are not.

Your sapphires, are very likely to be sapphires and very well might be treated like glass-filled or dyed, it may be possible you can see this in your scope. I only point this out due to your comments of readings inconsistent to each other and of course cheap.


Thanks again glhays.

You said: " (We use GIA)". I'm aware that with most things you get what you pay for and I figured it would especially apply here. So I found some used GIA equipment. This is what I purchased: Gem Duplex II Refractometer, GIA Utility Lamp & GIA Polariscope (extra lenses). It costs me 400 but compared to new it seemed like a good deal. My next purchase will be a decent specific gravity set up which I hope to buy soon, if not today.


Top
 Profile  
Reply with quote  
 Post subject: Re: Presidium Duo Tester II
PostPosted: Thu Sep 16, 2021 3:36 pm 
Offline
Site Admin
User avatar

Joined: Sun Oct 16, 2005 12:22 pm
Posts: 20987
Location: San Francisco
The accuracy of the scale for SG is paramount.


Top
 Profile  
Reply with quote  
 Post subject: Re: Presidium Duo Tester II
PostPosted: Thu Sep 16, 2021 7:13 pm 
Offline
Gemology Online Veteran
User avatar

Joined: Tue Apr 05, 2016 7:58 pm
Posts: 914
Location: San Marcos, CA
Yes agreed do not cheap out on the scale and find one that reads to .001-.003cts. and will fit under/over your specific sg setup. I typically only use for rough material and leave the heavy stress work to my gemologist. :)
Mineralab.com is a good source to start.

_________________
The Gem Garden
San Marcos, CA


Top
 Profile  
Reply with quote  
 Post subject: Re: Presidium Duo Tester II
PostPosted: Tue Sep 21, 2021 1:30 pm 
Offline
Established Member

Joined: Sat Sep 11, 2021 9:38 pm
Posts: 15
Location: Oxford NC
glhays wrote:
Yes agreed do not cheap out on the scale and find one that reads to .001-.003cts. and will fit under/over your specific sg setup. I typically only use for rough material and leave the heavy stress work to my gemologist. :)
Mineralab.com is a good source to start.


Mineralab is where I purchased the Presidium Duo. It does seems like a good place to start. I would likely use one of mineralab's SG set ups but a maybe a different scale. Possibly 1 digit better on the minimum weight to .0001 grams. Though I'm not sure how that converts to Ct? But I do see that going the extra digit often more than doubles the cost of a scale. All the gram lab scales I have seen also measure in Ct.

I have looked off and on for several days. I have noticed most if not all Lab scales use grams as the determining factor for their accuracy from .1 to .0001 and some even lower. The Swiss and German brands seem to be the most trusted and expensive. Ohaus, Sartoris, Mettler, Mettler/Toledo, Denver etc. A gently used Ohaus would be great!
But I also have to make sure whatever I buy will be compatible with the SG set up I purchase.


Top
 Profile  
Reply with quote  
 Post subject: Re: Presidium Duo Tester II
PostPosted: Tue Sep 21, 2021 6:41 pm 
Offline
Established Member

Joined: Sat Sep 11, 2021 9:38 pm
Posts: 15
Location: Oxford NC
Attachment:
Polariscope1.jpg
Polariscope1.jpg [ 168.96 KiB | Viewed 68 times ]
Roughwater wrote:
glhays wrote:
Yes agreed do not cheap out on the scale and find one that reads to .001-.003cts. and will fit under/over your specific sg setup. I typically only use for rough material and leave the heavy stress work to my gemologist. :)
Mineralab.com is a good source to start.


Mineralab is where I purchased the Presidium Duo. It does seems like a good place to start. I would likely use one of mineralab's SG set ups but a maybe a different scale. Possibly 1 digit better on the minimum weight to .0001 grams. Though I'm not sure how that converts to Ct? But I do see that going the extra digit often more than doubles the cost of a scale. All the gram lab scales I have seen also measure in Ct.

I have looked off and on for several days. I have noticed most if not all Lab scales use grams as the determining factor for their accuracy from .1 to .0001 and some even lower. The Swiss and German brands seem to be the most trusted and expensive. Ohaus, Sartoris, Mettler, Mettler/Toledo, Denver etc. A gently used Ohaus would be great!
But I also have to make sure whatever I buy will be compatible with the SG set up I purchase.


I made an offer on a used Ohaus .0001gram (.1MG) Lab Analytical scale. I am adding pics of the Polariscope and Refractometer and accessories I recently acquired. It came with a light, 2 extra lens and a 2x lens adapter.


Attachments:
Polariscope-Refractometer-etc.jpg
Polariscope-Refractometer-etc.jpg [ 179.68 KiB | Viewed 68 times ]
Refractometer-2x lens-light.jpg
Refractometer-2x lens-light.jpg [ 142.26 KiB | Viewed 68 times ]
Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 20 posts ]  Go to page 1, 2  Next

All times are UTC - 4 hours


Who is online

Users browsing this forum: No registered users and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group
Gemology Style ported to phpBB3 by Christian Bullock