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Did they use glass in the 60's and make fake Alexandrites


#1

I was wondering if anyone could help me. I inherited some “gem
stones” from my Uncle. They were all supposed to be glass. He
worked in the industry that supplied the fake semi precious
stones to higher end costume jewelry makers in the 50-60’s/

Last night I was looking at one stone I had mounted and it was I
thought an ameythst simulant. I went under florescent lights in my
kitchen and the darn thing turned blue.

Now, I know about Alexandrites…I own a few lab created ones. I
brought one out as a test next to this “stone”/ The lab Alex did
not change nearly as well as this “glass” one.

So, my question is…how can I tell what this so called glass
alexandrite is? Is there a simple test for glass, rather than lab
Alex’s. The color change is really dramatic. I am surprised I
didn’t see it sooner. I had it mounted in Sterling and put it on
an illusion necklace for sale. Now, until I know what this stone
is, I don’t want to sell it. The other glass amethysts in the
same lot as this one, did not change color in this way. Most were
amethyst colored stones.

So, did they use glass in the 60’s and make fake Alex’s??

I figure someone on this amazing group would have some

M.


#2

M, I can’t answer you about the stone, but I have some glassware
I inherited mother-in-law (I think she inherited it from hers,
but don’t know how old it is) that changes from pink to blue in
different light. A wonderful effect. Anyhow, perhaps one of
the glass museums (Corning?) might be able to point you in the
right direction.

Colene


#3

What you have there, probably, is a synthetic corundum (which
used to be known in the trade as synthetic alexandrite, but in
reality true synthetic alexandrite has only been developed
fairly recently). They often exhibited very strong color
changes.

Daniel R. Spirer, GG
Spirer Somes Jewelers
1794 Massachusetts Ave
Cambridge, MA 02140
617-491-6000


#4

Dichroic rhinestones (changing from light blue to light
lavender) were used in costume jewelry, I believe in the late
50’s and early 60’s. Most well known for this jewelry was a
costume company named Kramer of New York, which made (for the
most part) higher end costume jewelry. I also have some dichro
crystal beads, strung on chain, with this same effect, from an
unknown company. Diane in IA


#5

M, I don’t know anything about the stone called “Alexandrite”,
but there is indeed a glass simulant which has been made for
decades, probably at least since the 30’s. You see it a lot in
old glass beads from Europe which were made in that era; now with
the bead craze of the 90’s, they are being re-introduced as being
"Alexandrite" in color.

“Alexandrite” glass is what as known as “dichroic” (not to be
confused with the metallic glitzy stuff you see in handmade beads
these days). Meaning it has two colors, depending on the kind of
light it receives. Under fluorescent light its lavender blue;
under incandescent light it’s lavender pink. The difference is
dramatic. The molten furnace glass is colored with a rare earth
oxide called Neodymium. This is what gives it this unusual
color.

I don’t know how you might test whether this “stone” is glass or
a “fake Alexandrite”, but I do know that “Alexandrite” glass
exists and has been around for quite some time.

Rene Roberts


#6

It is important to realize the difference between imitation and
synthetic alexandrite. A synthetic has to have a natural
counterpart in order to call it synthetic, otherwise it is just
manmade. A synthetic has essentially the same physical, optical
and chemical properties of a natural, but produced in a lab i.e.
synthetic alexandrite chrysoberyl. A simulant is a look-alike.

Alexandrite simulants can be glass or other materials (i.e.,
synthetic color change sapphire) The syn. CC Sapphires tend to
change from a violet (w/green flashes) to pinkish purple. Syn.
alexandrite chrysoberyl is similar to the natural, green
(grayish) to red (purplish red). Glass (laser glass) usually has
the most pronounced color change, reds, greens, violets, purples
etc. They are doped with rare earth elements that cause these
color changes. Glasses and simulants have been produced for a
while, i.e., syn corundum (ruby) from the late 1800s.

If the color change of your stone is very strong, it may be
color change (CC) glass. But the judgment of strong is
subjective so testing the species of the stone is more
conclusive. Check the refractive index (RI) of the stone, and
the optic character (singly refractive vs. doubly refractive, SR
Vs DR). You’ll need a refractometer and polariscope to do this.
If you don’t use or have this equipment, find yourself a
gemologist to do you this favor. Syn Alex is DR, with a 1.746 -
1.755 RI. Syn CC Sapphire is DR, 1.762 - 1.770, and color
change glass typically ranges from 1.65 - 1.96 (over the limits
of the refractometer) but glass is SR. These two tests will
really help in your decision.

Just a note, the separation of natural alex from syn should be
made using microscopy, and using a competent gemologist who has
experience in these decision. Finishing a course does not
equate to being competent.

Later,
Arthur (a former GIA instructor, 7 1/2 years)


#7

How did they do a synthetic corundum? I believe this might be the
case, since my mom, who was a jeweler…got me a very large "alex"
in the late 60’s…it must be at least 14mm. I couldn’t begin to
tell you the weight. But the insurance claims it to be a color
change synthetic sapphire. Does that ring a bell?

Is this smaller stone worth going to a GIA or some one for
inspection? And if so, any ideas who to see?

thanks.


#8

Are you talking about the 1960s or the 1860s? Cheap synthetic
corundum and spinel have a history that dates back to around 1850
when a Frenchman named Marc Gaudin began trying to make synthetic
rubies (corundum). In 1904 August Verneuil introduced a technique
called “flame fusion” that gave birth to a flood of stone
look-alikes, including alexandrite.

It’s likely the “glass” your uncle referred to was a synonym for
"inexpensive." Many so-called “birthstones” were indeed glass
until recent years. But most of the “alexandrites” found in
jewelry like class rings are either flame fusion corundum or
spinel, not chrysoberyl. They have a dramatic color change, but
nothing truly resembling natural stones. They are still sold at
rip-off prices to unwary tourists in places like Mexico and Egypt
(Alexandria and all that).

Now, fast-forward a little. There’s a new breed of “luxury
synthetics” – emeralds, rubies, sapphires, alexandrites, etc. –
that’s vastly different from the flame fusion breed. Without
going into a lot of detail, these stones are grown over long
periods of time in labs by the flux, hydrothermal and Czochralski
"pulling" methods. They’re gorgeous, and they’re not cheap
(although far less dear than naturals). The new lab alexandrites
are mineralogically the same as chrysoberyl, and they exhibit
color change very similar to genuine alex.

Tests: glass doesn’t have a crystal structure. Unlike
crystalline minerals, it is warm to the touch. Glass also
usually shows round or elongated bubbles under magnification, and
the refractive index and specific gravity of glass imitations are
not usually anything like those of the gems they’re supposed to
be. (There are many other tests but I think R.I. and S.G. can
separate synthetic corundum or spinel from chrysoberyl very
easily, and that’s the test I think you should make. The
amethyst to blue change is a tip-off, typical of flame-fusion
corundums; the usual alexandrite change is from reddish-purple to
teal green or greenish-blue). If your stone is over 1 carat, the
chances are almost nonexistent that it’s genuine alexandrite.
People don’t “lose” real alexandrites. I spent the better part of
a week recently on my hands and knees, searching for one that
popped out of my tweezers. I found that puppy, too…there was
simply no other possible outcome.


#9

I remember my mother had some costume jewelry (probably pretty
inexpensive) back then; I recall particularly a pendant (or
brooch) she had, that had different colors on the different
facets when the light changed. But as I recall it looked like
just a surface effect (like we get nowadays by applying a very
thin metallic coating; different colors for different
thicknesses.)

Margaret
@Margaret_Malm


#10
   So, my question is...how can I tell what this so called
glass alexandrite is? 

I would suspect that your simulated Alexanderite is a flame
fusion synthetic corundum, this was, and still is quite
available.

   Is there a simple test for glass, 

Under dark field illumination you should be able to see small
gas bubbles and curved growth lines. The RI will be 1.77. This is
considered an easy determination for a trained gemologist.
WayneM


#11

Glass and other simulants go back a LOT farther than the 60’s.
While glass has been widely used as a simulant, it’s not the only
one. Glass could concievably have the color change you describe,
but it closely resembles some synthetic spinel I recall seeing
way back when, as well as some of the more common, synthetic
sapphire type of simulant. The latter is very common. This is
not “lab” alexandrite, since it is not chemically the same as
alexandrite. It’s color change goes from purplish/amethyst
color to a blue/grey color. The spinel version has a stronger
blue, and the purplish color under incandescent is redder, though
still purple.

Testing any simulant is sometimes easy, sometimes not. If you
can find spherical high relief gas bubbles in the material, it’s
usually glass or plastic. No natural gems have round bubbles of
gas in them. but glass manufacturers have gotton pretty good
and preventing these. And very old flame fusion types of
synthetic corundum, most commonly ruby, also sometimes have
spherical gas bubbles. You need a good loupe to see these
clearly. A penlight lighting the stone from the side or back
also helps a lot.

Glass also sometimes shows distinct "flow lines. These are
simply the syrupy curvy lines of flowing glass as it’s poured,
quite unlike the usually geometric or straight zones of color you
can find in real gems. Think of the appearance of honey poured
into water and not completely stirred. visible swirly streaks.
Glass and plastic and amber are the main things that can show
this. Again, easier to see with a loupe.

A definative identification usually needs examination with both
a polariscope and refractometer. The latter is expensive, but a
polariscope is just two pieces of polaroid held at 90 degrees to
each other. In that orientation, light coming through both will
be blocked, and you’ll see what looks like dark purple only, when
you look at a light through crossed polaroids (Like the lenses
from a scrap pair of cheap sunglasses, for example. You need only
rig up some way to hold then at 90 degree rotation to each
other, one above the other, with a space between in which you
hold your gem) Anyway, crystaline materials held between those
two polaroid lenses show interesting effects. Cubic system
materials, including spinel, garnets, and diamond, usually stay
dark looking, though often streaky. Glass gets a cross shaped
bright pattern that stays oriented to the polaroids, no matter
how you turn the gem. Most other gems, like alex, sapphire,
etc, as you turn them, they blink from light to dark. The
appearance of glass under a polariscope is fairly distinctive,
and easy to do. You do have to buy or make a polariscope
though. Commercially made nice units cost several hundred. But
like I said, you can put a couple saw slots in a scrap of wood,
and use those to hold a couple lenses from a pair of cheap
polaroid sunglasses, and though it’s a bit crude, it will work.

Of course, your best bet would be to simply take the stone in
question to someone with the ability to identify it. Most
jewelers, for example. Might cost you a few dollars for someone
to see if it’s glass, but that’s still easier than going to some
great effort to make a polariscope and learning to use it…

Hope this helps.
Peter Rowe G.G.


#12
 I remember my mother had some costume jewelry... I recall
particularly a pendant... that had different colors on the
different facets when the light changed. But... it looked like
just a surface effect  

You are probably talking about the “aurora borealis” coloration
that has appeared on costume jewelry since the '50’s or so -
purely a surface application - Mike