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R.I. testing?


#1

I don’t have a gemological background. I have a presidium duo
tester. This tests for thermally and refractively. There is a chart
on the side that lists different ranges of the RI meter, but I don’t
know what GGG,YAG, high zircon, and strontium titanate mean.

I was testing a alexandrite the other day… What category does
that fit into.

It would be great to have a chart or a book with all the stones
listed.

Brad B.


#2

GGG, YAG, and Strotium Titanate are synthetic materials with high
RI. ST is around 2.4 or 2.6 I think, yag is 1.83 as is GGG (I
think)… high zircon is another type of zircon (low and high zircon).

Alexandrite is a chrysoberyl I believe. Although it is synthesized as
corundum.

Craig


#3

GGG is Gadolinium Gallium Garnet, YAG is Yttrium Aluminum Garnet, I
assume something like “high zircon” would be a zircon with a high RI
or a CZ, strontium titanate is another synthetic.

GGG, YAG, CZ, znd strontium titanate are all synthetic materials
that have high refractive indexes, and have been used as diamond
substitutes at one time. YAG was the prefered diamond substitute
until CZ became easily available, just as moisanite seems to be
gaining more popularity than CZ now.

I dont think alexandrite would fit into any of those categories.
Does the tester actually show the RI, or only have those sypes of
materials listed as refrence?

A quick google search brought up this list as the first result. not
everything is on this list, but it should give you a general idea.

Mike


#4
 There is a chart on the side that lists different ranges of the RI
meter, but I don't know what GGG,YAG, high zircon, and strontium
titanate mean. I was testing a alexandrite the other day......
What category does that fit into. 

Alexandrite doesn’t fit into any of those listed. GGG, YAG, etc., are
all individual stones which are diamond stimulants. You don’t see GGG
and YAG any more, they were stimulants that were used before CZs came
out.

GIA has books and charts that list the RIs of stones. You get them
when you take a class. Check the GIA bookstore to see if you can buy
them separately.

http://www.gia.edu/geminstrument/shoponline.cfm

Elaine
Elaine Luther
Metalsmith, Certified PMC Instructor
http://www.CreativeTextureTools.com
Hard to Find Tools for Metal Clay


#5

Hello Brad:

   on the side that lists different ranges of the RI meter, but I
don't know what GGG,YAG, high zircon, and strontium titanate mean. 

GGG is Gadolinium Gallium Garnet. YAG is Yttrium Aluminum Garnet.
These stones are catagorized as Diamond simulants.

   I was testing a alexandrite the other day...... What category
does that fit into. 

Chrysoberyl

Order a book called “Gem Identification Laboratory Manual” from
www.gia.edu Does your tester say that you can get a RI on any Gem?

Presidium Duotester
Portable Diamond Testing with Thermal Conductivity and Reflectivity
measuring in the same affordable instrument. The Presidium Duo Tester
is the only tool on the market that provides the user with two proven
tests for diamonds and the ability to differentiate between similarly
coloured

Michael R. Mathews, Sr.


#6
    I don't have a gemological background. I have a presidium duo
tester. This tests for thermally and refractively. There is a
chart on the side that lists different ranges of the RI meter, but
I don't know what GGG,YAG, high zircon, and strontium titanate
mean. 

GGG is Gadolinium Gallium Garnet, YAG is Yttrium Aluminum Garnet.
Both are laboratory created, diamond simulants that have a garnet
structure. Gemologically speaking, they have no natural counterpart,
so are not referred to as synthetics. Strontium titanate is another
lab created material once commonly used as a diamond simulant.

High zircon is a zircon with a relatively intact crystal structure
as compared to low, or metaminct, zircon. In the latter, radioactive
elements in the material may cause a gradual breakdown of the
original crystal structure, making it nearly amorphous.

    I was testing a alexandrite the other day...... What category
does that fit into. 

Alexandrite is in the chrysoberyl family.

     It would be great to have a chart or a book with all the
stones listed. 

There are dozens of books available. Check your local bookstore.
Additionally, your Duo Tester does check diamond and its simulants
thermally, but not refractively, as you mentioned. However, it does
check reflectivity to some extent.

To be honest, you’re asking gemological questions while having no
gemological knowledge. You’re going to have a difficult time
understanding the answers to your questions until you make an effort
to at least look into practical gemology. A good place to start is
with a book like Gem Identification Made Easy. Good luck.

James in SoFl


#7
    I assume something like "high zircon" would be a zircon with a
high RI or a CZ 

CZ is not zircon, it is cubic zirconia, an entirely different
mineral from zircon.

James in SoFl


#8
Alexandrite is a chrysoberyl I believe. Although it is synthesized
as corundum. 

Alexandrite is indeed a chrysoberyl. There are man made Alexandrites
and they is an imitation made with corundum which has a different
color change. Real Alexandrite has a red to green color change. The
imitation, Corundum, has blue to purple color change as I remember.

Dan Wellman
Speedway Indiana
(Any race fans who come to the Indianapolis Motor Speedway?)


#9
    Alexandrite is a chrysoberyl I believe. Although it is
synthesized as corundum. 
   Alexandrite is indeed a chrysoberyl. There are man made
Alexandrites and they is an imitation made with corundum which has
a different color change. Real Alexandrite has a red to green color
change. The imitation, Corundum, has blue to purple color change as
I remember. 

There are man made alexandrites, and “THEY ARE” alexandrite, only
synthetic. Hydrothermal synthesis I think. (or was it supposed to
read “THERE IS”. That actually works better. As written, I’m
reminded of the old Pogo quote… “We have met the enemy, and they
is us”… Very true when it comes to typos and computers.) (forgive
me. I’m just pulling your leg… :slight_smile: )

And then there are imitation/simulated alexandrites of several types,
including the common color change flame fusion synthetic corundum,
which you describe. I’ve also seen a glass product with a color
change, and a couple other synthetics (possibly garnets of some type,
though I did not have a chance to test them) which had a color change
somewhat similar. So far as I know, only the true synthetic
chrysoberyl alexandrite has a color change range similar to the real
stuff, and of this synthetic material, all that I’ve seen tends to be
lower saturation, lighter colors, not the really intense dark tones
of the best natural material.

Peter Rowe


#10

=A0 =A0 =A0 =A0 I assume something like “high zircon” would be a zircon=
with a

=A0 =A0 high RI or a CZ

=A0 =A0CZ is not zircon, it is cubic zirconia, an entirely different
=A0 =A0mineral from zircon.

I understand that now. I have done a little reading since I
responded since I didnt have time to look into it when I first
replied. I was not sure about it when I first said it, and that is
why I said “I assume” because I do no tknow what materials testers
usually can seperate. I have heard refrence to some that will say if
it is CZ so I put 2 and 2 together assumed perhaps that was what it
was.

I too have no gemological background, and am only learning things as
I go. I try to be correct and speak from knowlege that I have gained
with experience, but sometimes it is wrong. When I am wrong, I am
glad that people will point it out to me so I can correct it. Thanks
for pointing out my mistake(even though I had already discovered it)
and next time I will make sure to not make the same assumption.

thanks,
Mike


#11

The least of being high zircon is natural where CZ has no natural
counterpart (simulant).

The differences between low, medium and high zircon are in their SG
and RI.

Craig


#12
    The least of being high zircon is natural where CZ has no
natural counterpart (simulant). The differences between low, medium
and high zircon are in their SG and RI.

Oh heavens to Betsy! It’s happened again! Someone has said there’s
no natural counterpart to CZ! But you know – it’s not true! If
there’s one thing we can’t stand on Orchid, it’s misSo
now we have to have the whole conversation over again.

Yes, Virginia, there is natural cubic zirconia. It’s exceedingly
rare and was discovered only after synthetic CZ had been created.

Elaine
Elaine Luther
Metalsmith, Certified PMC Instructor
http://www.CreativeTextureTools.com
Hard to Find Tools for Metal Clay


#13
I too have no gemological background, and am only learning things
as I go. 

Ok guys, this is why everyone needs a proper education. I am all for
self education (I am about 80% self taught for jewelry making) but
there are some things that need to be learned through a proper
educational institute like the GIA. Gemology is one of those things.
Until you have gotten yourself a proper education you should be
extremely careful about anything you say to anyone about this
subject. It’s great if you can learn what you need to at some point
on your own but there is a reason why educational institutes like the
GIA exist.

Daniel R. Spirer, G.G.
Daniel R. Spirer Jewelers, LLC
1780 Massachusetts Ave.
Cambridge, MA 02140
@Daniel_R_Spirer
www.spirerjewelers.com


#14

For those who would like a gemological education without investing
several thousands of dollars, may I suggest the International School
of Gemology. [http://www.schoolofgemology.com] It offers an
excellent foundation, all ONLINE! for less than 1% of the cost of the
GIA.

By the way, I am in NO way affiliated with the ISG; I just think
it’s one of the best values available.


#15

Elaine, you are right,cubic zirconia is a zirconium oxide. And, YES,
zirconium oxide occurs naturally (Baddeleyite: ZrO2: extrelmely rare
), but it crystallizes in the monoclinic cystal system. In order to
make CZ crystallize cubically in the laboratory, a stabalizer must be
added (calcium or yttrium). Therefore I think, technically, we must
consider CUBIC zirconia an artificial product.


#16
I too have no gemological background, and am only learning things
as I go. 

Please know that gemmology is a science and it is not about "sight
ID’ing something based on what it looks like. It is about using
knowledge to separate what you want to identify from other material
that looks similar. A characteristic or group of characteristics that
separates it from all other material that is so unique to that
material that it could not be anything else.

Please consider if your source is known by you to be a trusted
source, or someone passing on what they heard somewhere from
someone, a source they do not know as reliable.

The other day someone asked me about a stone, they wanted to know
what an “eisenhower” was. I replied it was a president and a tunnel.
She looked blankly back at me like I did not know what I was talking
about.

Today someone asked me "What is a green stone that starts with “h”.
When I start asking for details, she says she does not remember
anything about what it looks like.

Another lady tells me she wants a bracelet that matches her
transparent brownish black stone earring. She tells me it is a
citrine. I tell her it is smoky quartz, she replies that the guy who
sold it to her told her it was a citrine. I showed her a citrine,
and a smoky quartz and asked her which one it looked like, and she
pointed to the citrine. The citrine was yellow, the quartz was
brown. Go figure.

If you pass on misyou risk losing trust if the person
finds out the truth, and trust is what the jewelry business is based
on if you are going to be successful.

To me it is kind of similar as if any of you tried diagnosing
someone’s medical condition by hearing their symptoms, and you had no
medical training. A headache could be a sinus infection, or a brain
tumor.

My point is that I deal with misall the time, and it is
frustrating.

There are diamond dealers who use G.I.A. nomenclature and do not
know Vs, from Si, from I clarity. Kind of scary to me. I would not be
a victim of these people, but someone is.


#17
   there is natural cubic zirconia. It's exceedingly rare and was
discovered only after synthetic CZ had been created. 

Elaine is this published anywhere, I’ve never heard this before!

Wow…
Craig
www.creativecutgems.com


#18
The least of being high zircon is natural where CZ has no natural
counterpart (simulant). 

Synthetic CZ does have a natural counterpart that has only been
found as diamond inclusions. There has never been a deposit of
natural CZ, but it does occur in nature, however tiny the crystals
are.

The differences between low, medium and high zircon are in their SG
and RI. 

There are other differences. High and medium zircon may be
transparent colorless, blue, yellow to yellowish-green,
brownish-green, orange to brown or brownish to orangy-red. Low, or
metaminct zircon is transparent brownish- to yellowish-green with a
cloudy texture, and more rarely, brown or orange. In trade practice,
it is sufficient to identify it as zircon and specify it according
to color.

Another huge difference is birefringence. Birefringence is the
difference between the two refractive indices of a doubly refractive
mineral. Metaminct zircon’s birefringence can be as low as .000, or
singly refractive. High zircon’s may be as high as .059. That is
high enough to where you can actually see two facet junction images
when you look through the stone under magnification. Medium zircon’s
birefringence obviously falls in between.

Another difference is hardness. Low zircon’s hardness is 6, while
high zircon’s is 7.5, quite a range.

Since it has been mentioned, here are the specific gravity and
refractive index differences between high and low zircon for
clarity’s sake: SG varies from 3.90 (metaminct) to 4.73 (high). RI
varies from 1.810 - 1.815 (+/- .030) (metaminct zircon) to 1.925 -
1.984 (+/- .040) (high zircon).

James in SoFl


#19
 I am in NO way affiliated with the ISG; I just think it's one of
the best values available. 

Do others agree that the ISG training is good?

–Noel


#20
 Elaine is this published anywhere, I've never heard this before! 

This is from my GIA classes. I will poor through the binders and try
to find it in print.

Elaine
Elaine Luther
Metalsmith, Certified PMC Instructor
http://www.CreativeTextureTools.com
Hard to Find Tools for Metal Clay