A simple refraction test


2 things:

  1. Met with Jim Legge of Coppertop Gems yesterday and he brought his
    refraction testing gizmo and the stones tested as true. Good.

  2. A simple refraction test can keep me out of trouble? I will know
    that a stone is or is not genuine ( although not if it has been
    treated), right? If so, I’d like to buy one of these!

Anyone have a small used one for sale? Or, a recommendation for a
basic one?

thanks very much.
Marianne Hunter


Whoa! Refractive index measures the same with a true synthetic. IOW,
synthetic corundum, wheteher of the flame fusion type or Czochralski
pulled has exactly the same refractive index as natural material.
The same holds true for ALL synthetics.

RI is only one of the indicators that are used in determining the
nature of an unknown gem. Learning to recognize the types of
inclusions that occur in natural vs synthetics vs lab grown
simulants is one of the more reliable indicators, but many
synthetics and simulants are inclusion free.

Examination under a 10-30x microscope while the stone is immersed in
either water or benzyl benzoate or other heavy fluids will reveal
much about the structure. For example, hydrothermal corundum and
beryl quickly reveal a pattern when immersed in water that is
characteristic of those materials, and unknown in natural materials.

On the other hand, hydrothermal amethyst and citrine are VERY
difficult to identify as synthetic. Here, sophisticated means beyond
the reach of most jewelers must be brought into play.

If one were limted to a single tool, a GOOD spectroscope might be
the best choice, as it reveals the elemental make-up pf the stone,
which can be very revealing.

But, unfortunately there is no cheap and simple test that will
distingusih most synthetics from natural stones. As in the craft of
metal smithing, many skills, much knowledge and experience, and
considerable equipment must be brough to bear.

Some separations are simple, some are not, but, in the end, when
dealing with the public, a simple error can cost you your business
and much more.

Wayne Emery
The Gemcutter

Anyone have a small used one for sale? Or, a recommendation for a
basic one? 

Do yourself a favor and buy a new one.

Refractometers are easily damaged. If cylinder gets scratched, it may
render it useless.

Refractometer could give false results if liquid used for test is
applied incorrectly.

I would say that using refractometer without training is a waste of

Take a gem testing course and then buy the equipment. To know just
index of refraction is not enough for identification.

Depending on refractometer results, other tests are required.

leonid surpin

Met with Jim Legge of Coppertop Gems yesterday and he brought his
refraction testing gizmo and the stones tested as true. Good. 

minor point of nomenclature. It’s a refractometer. It measures the
refractive index.

A simple refraction test can keep me out of trouble? I will know
that a stone is or is not genuine ( although not if it has been
treated), right? If so, I'd like to buy one of these! 

The refractive index will help you identify what the material is,
such as quartz versus beryl or corundum, etc. It does not tell you
whether the material is natural verus man made, nor does it identify
treatments. All it does is help to identify what the mineral itself
is. After that, origin, treatments, etc, need other means of
identification. Often, a good microscope is the needed tool.

If you buy one, you will also need to learn how to properly use it.
It’s not a simple idiot proof device where you put the gem in and
push a button and it reads out the identity. It’s not overly
difficult to use either, but you do have to know how to use it. GIA
makes good ones, as well as teaching courses in gem ID which include
teaching the use of the refractometer.

Just a little opinion here. Others may disagree. But if you’re
making your living, or a substantial portion thereof, from the use
and sale of and your customers understandably expect you
to be at least a modest expert in the materials and gems you’re using
and selling, then for my money, I’d think you should see to it that
you’re not disappointing them. Learning gemology little bits at a
time in a haphazard and incomplete way, isn’t do you, or your
customers a lot of good. Better to take proper comprehensive courses
in the subject.

If you go to the doctor for a checkup, do you want it done by a nice
person who watched a doctor do it a few times, had a doctor show him
or her a few of the things to look for, and who read one or two
chapters of a book about such procedures? Or would you rather go to
an actual trained doctor?

If you’re expecting people to view and treat you as a professional,
it seems to me you should try to obtain professional level training.

And yes, I know this isn’t a universally held opinion. The percentage
of jewelers who owe their livelihood to gems, who nevertheless don’t
really know all that much about them, or whose knowledge of gems is
mostly hearsay, including both truth and misconseption and ignorance
all rolled together, is frankly quite astounding. It might be
forgiven that the college girl at the sales counter of the local mall
store who’s there as a seasonal holiday season temp employee, doesn’t
have any training about jewelry, but I find it harder to be that
charitable with people who are longtime career jewelers who
nevertheless seem to think they don’t need to actually know that much
about the stuff they sell. Their ignorance cheats themselves and
their customers, even if not deliberately so.

Peter Rowe


Testing a gemstone for it’s Refractive index on a Refractometer will
not tell you if it is Natural or not but it is one of the steps you
will find useful in making that determination. You may also want to
buy a Polariscope, a Specific Gravity liquid set and good

Greg DeMark

a refractometer can not tell the difference between natural and
man-made materials/minerals/gems. it can give you some data to assist
in determining the identity of the gem.

there are many gems with overlapping properties, so relying on one
test only is not a good thing.


I’m in solid agreement, but I’d like to say that I routinely repair
refractometer glass hemicylinders for their owners. GIA no longer
repairs theirs, nor will they replace the glass.

Best wishes…

Wayne Emery
The Gemcutter

A simple refraction test can keep me out of trouble? I will know
that a stone is or is not genuine (although not if it has been
treated), right? If so, I'd like to buy one of these!

Well no, its not that simple. RI reading is just one of several
things to help make a syn/gen seperation, sometimes.

What were the stones purported to be? Because that would make a
difference in how a gemologist would test. Example: the seperation of
synthetic from genuine sapphire would more commonly be based on
examining under magnification with correct illumination, their RIs
being so close that a small refractometer would pobably not give
CLEAR readings in the field. However if the seperation was one of
sapphire vs syn blue spinel, yes RI would make that distinction
quickly, along with a polariscope or dichroscope exam. Which is not
to exclude visual…always loupe or mic it. BUT, you need to KNOW
what you are looking for.

I’m concerned/confused…in your first thread about this you said
you had them independently tested and 2 out of 3 were synthetic, yet
he comes around with a refractometer and all is good with the world.
I assume its a refractometer, could have been a yikes! reflectivity
meter(barf). So you have two differing findings…somebody is wrong.
Do you know which? On what criteria can you reliably decide?

Met with Jim Legge of Coppertop Gems yesterday and he brought his
refraction testing gizmo and the stones tested as true. Good. 

What does that mean, really? “Tested as true”. If that is his
wording, I’d get another opinion. Well clearly, you need to anyway.
Gems don’t test as ‘true’, they test with particular findings which
are then interpreted according to a methodology.

I’m sorry if anything I’ve said ruffles your or his feathers, its
just, from this side of the counter, something is wrong and it still
needs to be cleared up.


If only it were that easy! A refractive index reading can not
separate natural from synthetic. Neither can it be relied upon as the
sole indicator in determining what the stone is. It can however be
used to determine what a stone is NOT. Usually. I realize this is an
oversimplification and I suspect you will get a flurry of responses
which will go into greater detail, but that is the crux of it.

Jerry in Kodiak

If gem testing were as simple as plunking a stone on a refactometer
and sayiny - yup thats a real one - all us gemmologists would be out
of business. I spent several $K on training - several more$K on
equipment one of which is a refractometer. I also have a geology
background, over 50 years of cutting and handling 1000’s of stones
and I still get stymied A refractometer is avery useful tool but it
is only one of many that I use - it is useless for any stone with a
RI of over 1.81 - diamonds, some garnets, zircons sphenes etc Then
there are the synthetics - it takes a certain amount of practce to
differentiate some of the common lab stones with only a
refractometer. Specific gravity liquids filtered light, polarized
light, microscope examination( a biggie0 all play a part in determing
the what is it of a stone - by the way the term ITS REAL has no place
in aproper stone description - lab grown stones can be REAL - they
are not NATURAL - educate your customers to the difference. I tell my
customers to - buy what they like - but know what you are buying -
whether it be lab grown or natural - I do not sell any stone that I
cannot back up with the facts. Having said that - it can get
interesting when you come across unknown locality cabbing material in
old unlabelled collections - one locality stuuff that has been gone
forever - jasper and agate become great catchalls to put things in
Hope you find agood refractometer - watch out for a heavily frosted
glass - the solution eats it over time - makes it hard to read and
then you need the skill to repolish it or pay some to do that.

Dave Barclay - recovering from ahip relacement surgery and raring to
hea for hills next spring - in B.C. where rubies, sapphires and
emeralds have been found in situ - working on the diamonds thing
Rochound /lapidary/ geologist/ stone dealer/ accredited gemmologist

I need to correct my error about RI. I had confused in my fuzzy
brain the very close but still different RIs of syn/gen emeralds for
the RI of syn/gen sapphire.

Duhhh, must be all that loud rock music and solder fumes of my youth
catching up with me. Yeah, that’s what we call it in polite
circles…solder fumes.

In addition to the refractometer, polariscope, SG liquids, and good
magnification, you’ll need to get RI liquid for use with the
refractometer. I’d also suggest you get a calcite dichroscope and a
Chelsea filter. You should also consider getting a dark field loupe
with an opening large enough for you to hold a ring mounted stone
inside and rotate it.

Dark field illumination will help you view inclusions not normally
seen with direct illumination from the top or rear of a stone. I’m
sure you’ve seen the menu boards in restaurants that are clear
plastic with the illumination coming from the edge; dark field is
similar to that.

A Chelsea filter, also known as an emerald filter, can help you
distinguish between some natural stones and their synthetic
counterparts, but not all of them. Take a look at this link:

A calcite dichroscope will assist you in identifying pleochroism in

Keep in mind that few tests, by themselves, will identify a
particular gemstone with certainty, but enough tests taken together
will eliminate most stones thereby making identification easier.

There is a book titled “Gem Identification Made Easy, Fourth Edition: A Hands-on Guide to More Confident Buying & Selling

by Antoinette Matlins and A. C. Bonanno which you might find helpful
in using your gem identification tools. Another is “Gem
Identification” by Richard Liddicoat. I found the “Gem Identification Laboratory Manual” from GIA available on Amazon. It’s a very good
reference, but kind of pricey.

Good luck!
Mike DeBurgh

I agree with Peter. Your best avenue is to take a course in gem
identification. As time goes on and treatments become more
sophisticated it becomes more difficult to make identification

That being said, the first steps in identification are observation.
Look at the gemstone critically and make note of the color(s),
luster, clarity (clear, opaque, semi-opaque, etc.), cleavage pattern
if visible, etc.

Mike DeBurgh


you can check the refracting index (specific for each stone group)
with an equipment named refractometer (mine is British). But you
can’t determine if was treated or not, and even if is a synthetic

PS. glass range if RI is huge and the same for most of the stones.

To determine the nature of a stone (and even if is natural) you will
need, several equipements and the most important
thing…experience…a lot of experience.

Get a refractometer, and a lot of filters (like Chelsea).

There are other things that you can do.

www.braziliangems.org preparing for Tucson

I want to thank all of you for your replies, which verified my gut
feeling and the little that I do know of the high end gem business.
I’ve spoken with GIA and I am sending the ruby to them for testing
even though it is cost prohibitive relative to the cost of a small

I made a very bad decision. I was overtired, I should not have let
someone I didn’t know even come out… Even when the dealer promised
he would take back anything not as represented. Unfortunately, today
he told me that GIA is wrong about refraction differentiating natural
from synthetic. That was a really bad sign!!!

Peter, I understand your p.o.v., but my particular business isn’t
based much on faceted stones. This is the first ruby I’ve purchased
in more than 15 years, maybe longer. Most of the cost of my work is
in the enamel/metal art and labor. Opals (particularly the boulder
varieties) are my stone of choice and I have a good feel for them.
I’m having a great time with Brazilian quartz which is so
interesting, and I really trust my sources. I use polished mineral
cabs for their color and patterns. I buy from a few people I trust,
cutters I know; almost without exception, people I have dealt with
for years. I should have followed my instincts and said no, instead
of giving a cold call a chance. He said I’d told him at a show that
he could call on me later, and I just didn’t remember one way or the

I imagine this is going to cause a storm of argument…can a person
be in a business that utilizes gemstones without being a gemologist?
My feeling is that it can work in circumstances like mine, if one is
careful, which I was not in this case. Using the example of the
doctor…some things require a greater degree of training than
others. You could, for example be a jockey without being a vet, or a
gardener without being a horticulturist. If my business was about
selling gems, it would be another story. It would be essential.

My lesson in this is to take my own advice given to those who ask
me: do business with established people you know and who have been
vetted by others you know. If something doesn’t feel right, it
probably isn’t. Marianne

Marianne Hunter


  1. In a case when someone calls and states, has you relate, that
    you’d said he could call you later, there’s no shame or
    embarrassment in saying “I’m sorry, I don’t recall that. I appreciate
    your call, but I already have gemstone dealers with whom I do
    business and I’ll stay with them.”

  2. There are plenty of people in the trade who are not gemologists.
    Chance are there are some in your area with whom you could make
    arrangements for their services when needed.

Even in a situation such as this where you may feel you’re on the
downside of things, there are always lessons to be learned to your

Good Luck!
Mike DeBurgh

My lesson in this is to take my own advice given to those who ask
me: do business with established people you know and who have been
vetted by others you know. If something doesn't feel right, it
probably isn't. 

Sorry to hear of all your troubles in this matter Marianne. Your
quote above is exactly right.

Another point which I would like to add is that dealers in stone
often don’t know what they have in hand. As this discussion has
demonstrated gem ID is very complicated and requires extensive
training. When my wife took her test for a G.G. thirty red gems were
laid out on a table and she had to identify each one without error.

Personally, I rely on my intuition. Not to identify stones, but to
judge the character of the person I’m interacting with.

Marianne I hope this is your last experience of this type.

Love and best wishes.

you folks are all so great! I appreciate all your advice and an
offer to test them for me. I hate to tell you, but I’m going to
stick with what’s working: mostly work with natural weird stones,
opals etc that I have confidence in and resume being very careful
from whom I buy.

I have a lot of material ready to work with for a long time to come.
At 60, I know myself well enough to know that I’m not wired to do
well in such courses or to actually perform all the tests just as

I’m going to send the one stone to GIA because their name should end
any argument. I think he would argue anyone else made a mistake.

I’ll let you know when I find out. Happy thanksgiving! Marianne

Hi Marianne,

I imagine this is going to cause a storm of argument...can a
person be in a business that utilizes gemstones without being a

Absolutely you can! I think a smart business person does what they do
best and builds a supporting cast of vendors, professionals and
possibly employees to fill in the gaps. The same way you hire an
accountant or send out your stone cutting. If you’re not a gemologist
all you need to do is find a trusted one to work with so you always
know exactly what you’re selling. I can tell you one true thing,
there are a lot more gemologists in the world than there are people
who can do the beautiful work you do. Nobody can do everything, there
is just so much to know and learn and only so much time in ones life.
You should focus on what you enjoy and what makes you money (ideally
there are the same thing).

Love your work,

I agree. I’ve been Designing and manufacturing jewelry for 25yrs.
and I am not a “certified” Gemologist. I just have smelt, touched,
tasted, dropped, broke, burnt, chipped, etc. THOUSANDS of gemstones
and have learned about them that way. You could say, Self Taught. I
believe the best way to learn is to get off the POT and jump right in