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Gemstone testing device


Hi everyone,

I have stone samples arriving from India from various companies next
week and I am looking for a reliable stone testing device.

I would like to verify the stones are what the manufacturers tell me
they are but, if that is not possible I at least want to identify if
I am looking at glass or synthetics. From what I have read that is
probably all that I could hope for unless I am dealing in diamonds
and other precious stones. I have a pretty basic knowledge of stones
and really need something simple that does the job.

I am working with the following gems quality stones

London Topaz
Rhodolite Garnet

All advice welcome
Thanks Tina


An interesting post, however, the samples are they free? they most
probably will be genuine, then the risks begins.

Oncethey have your confidence and 1st order money!! presumably they
want payment up front for aproper order, then you may find you get

It depends on the contract of purchase they ask you to sign. Now if
they are prepared to send your order and when your happy with it
then you pay for it, it might just be a possible safer option. Before
that, you have to do the math and compare what it costs to import as
opposed to buying from a well known US stone supplier.

Normal common sense in fact.


The device you are looking for is called a gemmologist.


lol, Thanks for the chuckle. Maybe one day they will have one device
that can identify gemstones and quality but until then you need to
go to a gemologist. There are several devices that are used.


Thanks for the feedback.

I agree, its a risky business. A tester that could identify glass
and Synthetic materials would be very helpful to me. An ideal
situation would be to only pay for orders when the stones have been
delivered and tested but, at this early stage of my business
realtionship with these companys they are not willing to take that
risk. I have only known one supplier willing to do that and that was
because I had been recommended to him by a customer who had been
dealing with him for many years.

The samples are free except for one supplier, I paid half down and I
will pay the rest when they arrive. He would not start production
until he had some assurance that I was genuine. He has a good
reputation and the quality looks good so, I made an exception and
ordered quite a few samples.

I buy thousands of beads every year i I will be buying a lot of cabs
too so hiring a gemologist is just something I cannot afford. I of
course attempted to source my cabs here but, I could not find the
sizes and shapes I wanted. Dome heights and calibrations were not
guaranteed either so, I went straight to the source.

Can you recommend a tester that will help me identify glass and

Thank you for all your comments, they are very helpful.


As has been previously stated, you need a gemologist. Contact me
offlist for about this. John at rasmussengems dot com




To solve your gem identification problem, you may wish to invest in
"Gemstones of the World" by Walter Schumann, which lists all the
properties, (or find a chart of refractive properties of
the most common gemstones), a refractometer, with an appropriate
lighting source, and while you’re on the GIA store site, you may want
to look for any refractometer training specific literature. Also
there’s some instructions on using a refractometer on Utube. I would
also acquaint myself to the birefringence of as that is
one the most distinguishing aspect for ascertaining glass vs stone.
You could study the Hodgekinson method, originally discovered while
he was a nighttime cab driver between customers, where he learned to
use a single street lamp to identify gemstones (easier with faceted
stones). Either way, to acquire without paying an expert
who’s been suitably trained and tested, you will have to acquire
these skills yourself.

If you want calibration, the no one excels the German gem cutters.
You can find them at Tucson, or try to contact them in
Idar-Oberstein, Germany. Don’t have a connection right now myself.

MJ St. Amand (gemologist)



It would be nice if there were, but there is no such instrument that
will ID stones, separating naturals from synthetics, etc. There are
instruments which, when used by a knowledgeable person, can aid in
identification however. The catch is obtaining the knowledge and
also the experience. There are stones on the market now which can
only be separated from naturals by sophisticated equipment costing
perhaps a hundred thousand dollars.

Basic instruments used by gemologists to identify gemstones include
a loupe, gemological microscope, polariscope, dichroscope,
refractometer, specific gravity liquids, etc. There are others. None
of these will tell you what you want to know by themselves, but each
will provide a piece of the trained and experienced
person can use to help them identify a stone with a fairly high
degree of accuracy.

There are many sources from which you can obtain the necessary
training if you are so motivated. Google GIA (Gemological
Instituteof America), for one. IGA is another one you can access on
line. Hope thishelps. Good luck.

Jerry in Kodiak


Hi Mellisa,

I am not trying identify quality, and if I cannot identify the
actual stone, that is fine too. My main aim is to identify glass and
resin and other synthetics. Any ideas?

 I am not trying identify quality, and if I cannot identify the
actual stone, that is fine too. My main aim is to identify glass
and resin and other synthetics. Any ideas? 

__Tina, inspect under magnification. If it’s glass there may be round
bubbles. May also be “swirls”. If you check it with a polariscope, or
improvise one using crossed polarized lenses and it will not "blink"
It would be an amorphous substance and therefore probably not a
gemstone since most gemstones will blink. You will have to learn a
little bit about gemology atleast to understand some of the
terminology. Use a hot point, a heated needle will work but a small
electric soldering iron is better. If you touch it with the hotpoint
and it melts and gives off a chemical sort of odor it’s plastic.

Tina, what you are trying to do is gain knowledge without expending
any effort to gain it. What I told you above is a very minimal, quick
and dirty answer for you but there is much more you need to learn to
do what you want to do. The internet can be a big help for you. Just
go to Google and start asking questions. Enter something like “How
can I tell glass from real aquamarine?” and just follow where it
leads. You say you don’t need to know quality nor if a stone is
synthetic or natural. Well, you do need to know that if you are
paying a natural, good quality, price for a synthetic stone, andyou
definitely need to know the difference if you are going to sell it to

Jerry in Kodiak


Tina, You could ask the suppler to give a test certificate along with
the respective parcels.

Warm Regards,


Thanks to everyone who answered my enquiry.

I would especially like to thank MJ St Amand Your contribution to my
enquiry has been incredibly helpful. I will do exactly as you have
suggested. I will dedicate time to educating myself on how to use a
refactometer and then make the purchase. I need to have the means of
testing close to home and on hand. Thank you for taking the time to
contact me. Your has been very valuable.

Umesh, the problem is that certification is not available for
semi-precious stones and even if it was. If I cannot trust the
suppliers to provide genuine stones I cannot really rely on them to
produce authentic certification.

Lee Horowitz, thank you so very much for all the you
provided. It has been very valuable and educational. I will
definately buy a refractometer. It is exactly what I have been
looking for. Thank you very much! and thanks for your contact

Thanks Lara Scarberry.

Lois, I will be in touch with you.

Thank everyone
Best wishes


I don’t think the answer to this question is necessarily buying a

There are many ways to ID and separate gemstones and many are
cheaper and faster than using a refractometer. What is needed is some
gemological knowledge, as some have already stated. Depending on the
question asked, a little reading may be enough. For example,
identifying iolite should be easy enough. I don’t believe there is a
synthetic iolite, and I don’t think there is any other stone with the
specific dichroism which iolite exhibits. Looking at the iolite from
all angles, one should see a blue, a violet blue and a straw yellow
axis. I don’t believe any other stone shows this phenomenon.

As far as Tina’s other specific questions, there was a recent thread
on IDing natural vs synthetic amethyst which she should read.
Basically a refractometer will tell you nothing here, as synthetic
and natural have the same RI and birefringence and dispersion.
Magnification might show telltale inclusions of natural or synthetic.
Twinning suggests natural, as shown by the polariscope, but there are
now some synthetics with twinning. If no IDing inclusions are seen,
there is no cost effective way to tell natural from synthetic, as the
lab tests require sophisticated equipment and are very expensive.

Peridot is pretty easily identified by it’s dichroism and doubling
of back facets under magnification. It could be confused with green
zircon, but a Chelsea filter will differentiate the two.

Blue topaz is distinguished from blue zircon by the zircon’s doubled
back facets and from aquamarine by the dichroscope. From glass by
bubbles in glass. Blue synthetic spinel shows no dichroism.

The rhodolite garnet may show needles and other inclusions, will be
inert under the Chelsea filter, and may show anomalous double
refraction in a polariscope. A glass imitation (of garnet or any
other crystal) will be warm to the tongue compared to a crystalline
stone. Also garnet has more heft than most glasses.

The problem with the “buy a refractometer” response is that it does
not identify anything with an RI over 1.81, which encompasses several
synthetics, and it does not distinguish between synthetics and their
natural counterparts in most cases. GIA refractometers are not cheap,
and a good loupe with a dark light source, along with a Chelsea
filter, dichroscope and polariscope, will be much cheaper. If you buy
a cheap Chinese refractometer, you will need to make sure it is
accurate by testing it with quartz and some other stones with
constant, invariant RIs.

Someone suggested learning the Hodgkinson method and IDing with no
instruments at all. This is a great approach, but the info on it is
hard to find and one really has to understand what’s happening beyond
the “go-no go” approach of using a few simple instruments to do
specific separations.

Another simple approach with loose stones would be to learn how to
use a small digital scale with a tare function (about a $20 item)
along with a small condiment cup of water and a piece of string to
determine specific gravity. Quick and painless and a lot cheaper than
a refractometer. Weigh the gem suspended on the string in the water,
then tare the water in the cup at zero and weigh the stone by
allowing it to rest on the bottom of the cup in the water.

Then make the SG calculation. A lot easier than learning to use a
refractometer well, and no stones over the limit. Refractometers are
great when you don’t know much and want to use a look-up table and
when there is no synthetic with the same RI or material with a near
or overlapping RI. Also when the stone is mounted so that an SG
reading instead is impossible.

Another problem with “buy a refractometer” is that the OP’s needs
may change, and some questions would eventually require some
gemological knowledge. A good starting point for this would be
Antoinette Matlins’ book, Gem Identifaction Made Easy, now in its
third or fourth edition. Lots of used copies around.

If you really want to understand gemology, Wm. Hanneman’s Guide to
Affordable Gemology
will teach the thinking person all they need to
know better than any of the more traditional gemology texts.

The place to ask gemology questions of the experts is at the
Gemology On Line forums. Dr. Hanneman and other experts hang around
there. Sorry to be so long winded, but the specific answers to
gemological questions are often a little more involved than “buy a
refractomter.” That’s like telling somebody who wants to make jewelry
to “buy a torch.” Uh, well, yes, maybe, but…


Hi all

save yourself the hassle and buy from a quality gemstone dealer.

Mine O’Neills Affilated is a trade only supplier and each stone
comes with complete disclosure.

All the best


You are going to have a real struggle in using a refractometer. They
are designed to be used with flat polished surfaces and a bead
rarely has one - or at least one large enough. Sometimes it’s
possible to see a very faint shadow on the dial - but it will take a
lot of experience.

If you really want to understand gemology, Wm. Hanneman's *Guide
to Affordable Gemology* 

Oops, sorry, Roy. Didn’t read far enough. I agree that specific
gravity gives more for the cost than most anything else.
Of course, neither specific gravity nor refractive index will
distinguish between synthetic and natural material.

Al Balmer

Someone suggested learning the Hodgkinson method and IDing with no
instruments at all. This is a great approach, but the info on it
is hard to find 

I’d suggest Dr. Hanneman’s book, available at

and one really has to understand what's happening beyond the "go-no
go" approach of using a few simple instruments to do specific

True. It’s not a magic wand.

Al Balmer


Hi Tina,

I am not trying identify quality, and if I cannot identify the
actual stone, that is fine too. My main aim is to identify glass
and resin and other synthetics. Any ideas? 

Why are you buying gemstones from people you obviously don’t trust?
Wouldn’t it be easier to buy from trusted sources? Seems like it
would be cheaper too when you factor in the cost of equipment (a
quality refractometer and the required light source aren’t cheap) and
the time you’ll have to invest in learning how to use it and then to
identify each and every stone. These are expenses that you can’t
easily pass along to your customers as part of the legitimate cost of
known especially lower cost stones like you listed in your
first post.

It’s also important to understand that while a refractometer is a
handy thing to have around, it’s by no means a foolproof tool for gem
ID. It can’t tell you if a stone is a doublet or a triplet, nor can
it detect clarity enhancements like telling you if ruby is
glass-filled. Nor can it differentiate between many synthetics and
their natural counterparts; corundum (sapphire and ruby), beryl
(emerald) and quartz (amethyst) in particular. It can’t tell you if
something’s been heat-treated or irradiated either. All a
refractometer really does is measure how much the tested material
bends light at the tested surface. There’s a lot more to gem ID and
enhancement detection than that.

Another thing to consider. If you misidentify a gemstone, or fail to
find an enhancement or decide something is genuine when it’s
actually not and then sell it, YOU are the one that will be held
responsible. Not your guy in India.

I’ve been in the business for longer than I care to admit. I have
gemological training, access to a Graduate Gemologist (my wife), and
I own a fully equipped gem lab. I would never buy from someone that I
thought might be selling me fake or enhanced gemstones without
disclosing the facts. I can’t imagine why anyone would even consider
taking that kind of risk, especially with no gemological training or

Please reconsider your sources!

It’s pretty easy to find quality vendors and gemstone dealers. Just
ask here! You’ll get several very reputable recommendations. Starting
with Stachura.

Dave Phelps


Hi Everyone,

Just out of curiosity. If you did want to have gems tested.

Who would you recommend and how much can one expect to pay?

As always, love orchid and thanks for the advice!


Hi Everyone,

Just out of curiosity. If you did want to have gems tested.

Who would you recommend and how much can one expect to pay?

As always, love orchid and thanks for the advice!