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Amethyst?


#1

Good day to all in Orchid land Can any of you rock hounds, GG’s or a
more knowledgeable person than myself explain why an amethyst (at
least that’s what I thought it was), that has been coated with heat
shield, lots of it, would turn clear for a repair? I have used heat
shield before on amethyst’s with out a problem . Since the color
was not real dark to begin with but I thought heat would make it
darker not clear. Is it safe to say that it was never an amethyst?
Thanks in advance for your responses.

Barbara McLaughlin


#2

Barbara - Not all amethyst(s) are “born” equal. That’s the easiest
way to say it: much of the non-synthetic amethyst out there today
has already been heat treated long before you see it; some argue
that Nature heat treats the truly natural product. This plays into
the issue of disclosure, and what constitutes gem treatment. In any
event, where ever possible, I remove amethysts before soldering
because the purple coloration is not stable in all temperature
ranges.

Jim Small
Small Wonders


#3
    Can any of you...explain why an amethyst (at least that's what
I thought it was),  that has been coated with heat shield, lots of
it, would turn clear for a repair?  

Barbara: In short, heat turns amethyst into citrine. Exposing an
amethyst to heat causes it to lighten in color and then, with
sufficient heat, to turn yellow. Labs use this technique to create
ametrine.

I have learned the hard way to be very careful. During the final
polish of a carved amethyst, on a polymer pad charged with 50K
diamond grit, I watched a section of a cab turn clear before my eyes
when I was careless enough to let it heat up.

Michael Conlin


#4

Amethyst will not stand up to heat. Almost all citrine on the market
is amethyst which has been heat treated. I believe it’s somewhere in
the 400 degree C range that the color changes to yellow. Higher than
it disappears entirely. Marc Liccini’s site <www.liccini.com>
contains a wealth of on heat treating a whole variety of
stones.

Cheers
Hans Durstling
Moncton,
Canada


#5

All, In the book by Kurt Nassau he explains in great detail the heat
and radiation sequene of quartz, including amethyst. All amethyst
will not heat treat to citrine. Some will go straight to clear
quartz. Many treaters I have talked to have told me all amethyst is
heat treated. The treatment if done correctly is not detectable.
How much heat is a closely gaurded secret that varies for each mining
location. Amethyst is heat treated to lighten the color which is
often too deep. Any time you heat a quartz you take a chance of
changing the color. So torch away and take your chances. I have cut
many replacements for stones that have changed color or been broken
by the torch. Torch on.

Gerry Galarneau
www.galarneausgems.com


#6
           Good day to all in Orchid land Can any of you rock
hounds, GG's or a more knowledgeable person than myself explain why
an amethyst (at least that's what I thought it was),  that has been
coated with heat shield, lots of it, would turn clear for a repair?
 I have used heat shield before on amethyst's with out a problem . 
Since the color was not real dark to begin with but I thought heat
would make it darker not clear. Is it safe to say that it was never
an amethyst? Thanks in advance for your responses. 

Amethyst, when heat treated, first turns clear, and in some cases,
pale green. With further heating, it turns to citrine.

Heat shield is an aid to heat protection, but not fool proof. It
acts as a heat sink, but only if you’ve got enough of it that it
doesn’t dry out, in which case the water content of the stuff is
what’s keeping your stones cool. It’s other function is to
physically block contact with your stone from the direct flame. But
if the compound dries out too much from perhaps prolonged heating,
then while it may prevent direct flame contact, it will still allow
the stone to warm up. It’s more likely to survive without cracking,
since the shielding will help prevent sudden heat shock, but it still
can get plenty hot. And that can easily alter the color.

In general, use heat sheild only as a last resort. It’s such a
thick paste that any heating of the metal under it quickly dries it
enough that it can shrink away from the contact with the hot surface,
at which point it’s cooling effect stops, allowing heat to travel
further into the area contacting the stone. It’s sometimes the only
way to work on a piece without removing a stone, but it can be tricky
stuff. When you use it, the more you use, the safer it will be thin
films don’t do much but protect the surface from direct contact with
the flame. Better, if you can do the work with the stone in this
position, is simply to set a small cup of water on your soldering
station, and immerse the half of the ring(etc) with the stone under
water, leaving the portion to be soldered above water. Because it’s
liquid, any water evaporated by contact with hot metal is instantly
replaced, so the stone is still cooled by the water, never getting
significantly above the boiling point of water, which is still a
safe temp for amethyst. Variations are using a container filled with
sand, which is then saturated with water, or a wad of cotton or
tissue paper soaked with water, wrapped around the area to be
protected. In both cases, the water can still flow back around an
area, even if the sand or tissue isn’t in direct contact.

Hope that helps.
Peter Rowe


#7

Just a note to add to Jerry’s informative notes on heat changing the
color of amethyst, SUNLIGHT can also affect a change in amethyst. I
have seen clusters that sat in a store window both darken and lighten
in color. They can be sitting side by side and one gets darker, the
other lighter. Of course the lightening seems to happen much more
often than the darkening. So beware if your displays are in a sunny
window as other stones may be affected also.

Karen Bahr “the Rocklady” (@Rocklady)
May your gems always sparkle.


#8
 Barbara: In short, heat turns amethyst into citrine. Exposing an
amethyst to heat causes it to lighten in color and then, with
sufficient heat, to turn yellow. Labs use this technique to create
ametrine. "         Michael Conlin 

Dear Michael, I would respectfully like to correct you on the above
statement. Ametrine although once thought to be “lab created” has
long ago been proven totally 100% natural. When it first appeared on
the market in the early 1980s the suppliers did not want to reveal
their sources or the location of the mine. This fostered all sorts
of rumors as to it’s authenticity. As time has marched on the source
in Bolivia has been revealed and many beautiful natural ametrine
specimens in their natural state have made it to market. It is the
only mine in the world that produces this combination of citrine and
amethyst within the same quartz crystal straight from the ground in
an untreated state.

Steve Green / Rough and Ready Gems
For ametrine and other briolettes give me a jingle
www.briolettes.com


#9
 much of the non-synthetic amethyst out there today has already
been heat treated long before you see it " Jim Small 

I respectfully disagree with the above statement. Although it is
possible to lighten overly dark amethyst with heat treatment, it is
not practical nor is it done even in a small percentage of the time.
It is difficult to control and the value of the material does not
warrant the effort. Especially considering the low price and
quantity of synthetic amethyst on the market. Even the best natural
material is not that expensive in the rough.

By and large (99% of) the amethyst on the market is either totally
natural and not treated or completely 100% synthetic (as in
laboratory grown). It is not hard to tell the synthetics in stones
over 1 ct by their lack of natural growth features (twinning and
appropriate color zoning). However in many cases due to it’s low
price the effort to identify synthetic material is foregone.

This is a problem that the trade faces. Know your sources, and ask
them to show you the identifying natural characteristics of the
stones they are selling. If the stones are small or cheap, and do
not warrant this effort… beware it could come back to bite you.

Steve Green / Rough and Ready Gems
ex-amethyst miner and colored gemstone briolette source
www.briolettes.com


#10

Hi Steve, As an addendum to your comments on Bolivian ametrine ( I
wholeheartedly agree with your comments ) let me point out that the
citrine from the ametrine mine has the unique capacity of reverting
to amethyst with heat treating. Ron at Mills Gem, Los Osos, CA.


#11

Dear Steve. Quite right. Ametrine seems to be a one-source stone.
I am very interested in obtaining good quality, 50/50 color split in
gemstones of 125ct to 200ct size. Do you have source? Look forward
to your reply. Stephanie


#12

Steve:

Thanks for sharing. Your confident statement of your views is
commendable. Regrettably, I find that I am not as certain as you.

First, I am not certain, but I believe I did not say ALL (caps added
for emphasis) ametrine comes from labs. Rather, I believe I said labs
create ametrine. In my defense I will offer Caltech’s opinion that
"commercial production of ametrine takes place in a factory at
Alexandrov, Russia." [see URL
http://minerals.gps.caltech.edu/AMETRINE/Index.htm ] Is Caltech wrong?
I’m not certain; I haven’t been to Russia to check for myself.

Second, you state that “Ametrine although once thought to be “lab
created” has long ago been proven totally 100% natural”. Alas, the
Conservation and Survey Division of the Institute of Agriculture and
Natural Resources at the University of Nebraska-Lincoln, claims that
"The first ametrine was actually produced in the laboratory by
treatment of heat and irradiation." The article goes on to discuss
naturally occurring ametrine and how it differs from the laboratory
produced material which used Brazilian amethyst as an input. [see
URL http://csd.unl.edu/csd/birthstones/amethysts/amethyst.html ] Is
UNL wrong? I’m not certain; I haven’t been there to check their
research for myself.

Third, you state that the Bolivian mine “is the only mine in the
world that produces this combination of citrine and amethyst within
the same quartz crystal straight from the ground in an untreated
state.” Yet there are plenty of suppliers claiming to sell ametrines
from multiple sites in Bolivia, Brazil, Russia, and other places. Are
they lying about the source? I’m not certain; I haven’t been to their
mines to check for myself. Nor have I verified their audit trail and
inventory control procedures from the mine to the sales table.

Oh yes, my thanks to Gerry Galarneau for sharing his thoughts and
experiences on Quartz Treatments.

Regards,

Michael Conlin


#13

All, I would like to sit corrected (I’m at my computer) on my blanket
statement that most dealers assume all quartz is heat treated. This
statement is erroneous when applied to varieties of quartz other than
amethyst, citrine, and ametrine. Another blanket statement is that
other varieties of quartz except smokey are not treated. This list
would included, rutilated, clear quartz, strawberry quartz, and all
the others. Smokey can be natural or it can be irridated. Another
variety that is treated is the smokey and citrine combination. I
have been told that in Brazil they take amethyst crstals and heat
them to citrine then put one end into Barium salts which are
radioactive and change the buried end to smokey. Blanket statements
are very useful in science because the statement spurs rebuttal and
expands the learning of all involved. In science it is not unusual
at all for one blanket statement to be replaced by another after the
first has been reviewed and rebutted with good evidence not just
hearsay. That is why I use them and I will be the first to expand
them or narrow them when good arguments to the cotrary are adequately
supportted. My main point about amethyst, citrine, and ametrine is
why should it matter if a they have been heat treated by man or by
nature. We should all be telling the public that heat treating of
amethyst, citrine, and ametrine is an acceptable practice. Heat
applied to these crystals is a very low heat compared to other heat
treatments (300-500 degrees F) that is undetectable and in no way
affects the durability of the gemstone. Heat treatment makes the
stones brighter and more enjoyable to the buyer. The real issue with
amethyst, citrine, and ametrine is the amount of synthetic on the
world market. I have heard estimates from different dealers that
handle large amounts of these materials that over 50% of what they
see in cut stones is synthetic. What has everyone else heard.

Gerry Galarneau
www.galarneausgems.com
@Gerry


#14

Dear Michael. Do you happen to know how I could contact some of these
suppliers of ametrine that you mentioned as “multiple sites in
Bolivia, B razil and Russia.” Am interested in very large size
(100ct plus) stones with a 50/50 split, but the only source I know of
is the mine owner in Bolivia w ho is extremely pricey. Would
appreciate any leads you may be able to give me.

Please e-mail me at @stephanie_young Many thanks.
Stephanie


#15

Gerry, I have heard the same estimates for the amount of synthetic
amethyst out there. Although I must say, I’m beginning to wonder if
the figure isn’t taking on a life of its own: that 50 percent number
has been quoted to me pretty steadily for 10 years. I’d have expected
it to fluctuate a bit with amethysts ups and downs in the market, the
emergence of Russia as a source for synthetic stones, etc. I wonder
if it isn’t reaching the point where people are repeating it
continually, without reassessing or any particular knowledge.

But whether its 30 or 40 or 50 or 70 percent of amethyst is
synthetic, suffice to say, there’s a lot of it out there. The volume
manufacturers aren’t going to make the effort to detect it: it’s too
much effort for a relatively low-cost stone, and the effort would
have a major impact on price point. If you’re dealing with the big
retailers, a shift up in price point would almost certainly cost you
the sale to someone who wasn’t so picky about their amethyst. Plus,
there’s been no consumer outrage over it… and not because its a
well-kept secret. My hunch is just that it’s not expensive enough for
the “news” shows to get hot and bothered over it when they have gold,
diamonds, and pearls to flog.

I’d be curious, though, if QVC has picked up on the amethyst thing:
their quality control is legendary – all right, mostly becuase they
can be incredibly picky about minor flaws while allowing major ones
to walk right through – but they are fussy about their gems. And if
synthetic amethyst is that common, they’ve got to be seeing a lot of
it. Wish they were speaking to me: I’d ask. :slight_smile:

Ah, well… just some musings on a warm summer morning.

Suzanne
Suzanne Wade
writer/editor
Suzanne@rswade.net
Phone: (508) 339-7366
Fax: (928) 563-8255


#16

Suzanne,

There is no way of knowing how much amethyst is of synthetic origin.
It can be detected only with very costly procedures thereby making
it uneconomic.

On the other hand, most natural amethyst has characteristic flaws
which may not impinge upon its face-up appearance, but, nonetheless,
can be discerned by the casual observer using low magnification.
Much natural amethyst has color banding. This banding is usually
oriented parralel with the table and is usually aligned just under
the girdle.Color banding aligned this way will diffuse the stone
which rich hues even the remainder of the stone may be sub-par
colorwise. When this pehenomenon is present it is usually easily
seen by looking at the stone sidewise. Other characteristics of
natural amethyst are inclusions, some of which can only be seen
under magification. There are the feathers similar to those in
diamonds and there are mineral inclusions such as goethite, hematite
and lepidocrosite. The mineral inclusions are usually aligned with
the planes of hexagonal crystallization.

When attending a show,one of the dead giveaways of synthesized
amethyst are the trays of cuts stones that are exactly alike.
Coloration in natural amethyst is infinitely variable and even those
stones which have been graded for color will have minor variations
to the trained eye. Treatment of amethyst is a non issue and when it
is done, it is usually because the material is too dark. Excessive
coloration is not the problem in amethyst mining…insufficient
coloration is the problem and that is not a problem that is
economically feasible to treat. Natural amethyst is mined in
prodigious amounts. It is a major industry of course in Brazil and a
VERY major industry in Zambia. The Zambian producers employ hundreds
of people just to cob the output. Ron at Mills Gem, Los Osos, CA.


#17

All, Thank You Suzanne for your comments. The reason mhy I ask this
is because I do not know the answer either. Before I stopped repair
work last year I would have around 100 amethysts and citrines through
for replacement or repair a year. I would estimate that at least 75%
of these stones showed no zoning, no flaws, and no twining. Most were
in the 10+ carat range. I would identify them as synthetic, but the
customers all sent them to me as natural.

I also have seen natural quartz crystals from Brazil that had no
zoning, no flaws, and no twining. So how can I tell the difference?
AGTA came up with a scanning spectrophotometer that could separate
mass quantities of natural quartz from synthetic. I asked them what
quality of the gemstones this machine measured to determine whether
the stone was synthetic or natural. I asked them how they
standardized the machine to certify that it was reading properly and
making the correct identification. I received no answer and I have
not heard anything back since the initial press release. I would
really like to know what this machine measured in the stones to make
the determination of natural vrs synthetic and how accurate is the
machine. These are questions that should be answered by labs like
AGTA and GIA but the subject has been silent while tons of quartz are
sold in the USA every year. I wonder how much is sold world wide?
Last year I recieved a report that a huge parcel (I think it was over
3 million carats) of synthetic amethyst and citrine cut stones
entered the USA through British Columbia, Canada. The price on the
parcel was 8 cents per carat US Dollars. This year I have heard of
several smaller parcels entering the USA ( 100,000 carats) at about
18 cents per carat US Dollars. These figures have come to me
through the small group of dealers that handle this large of a
parcel. I am not saying these dealers sell synthetics, just that
they have been offerred these by their suppliers at these prices.
Again this is all second hand Does anyone have any
solid numbers that they are willing to share?

Gerry Galarneau
@Gerry
www.galarneausgems.com


#18

Hi Gerry, and all!

I think the key question at hand is: If synthetic quartz gems are
indeed so prevalent, how can one determine whether stones are
genuine? Of course, you could look for flaws that wouldn’t be in a
synthetic gem… but they would also be undesirable in a fine quality
genuine gemstone. Would one need a full blown gem lab, or is there a
pocket sized filter or scope that can differentiate most fakes
(recognizing there will always be exceptions)?

Any G.G.s out there care to enlighten us?

All the best,

Dave

Dave Sebaste
Sebaste Studio and
Carolina Artisans’ Gallery
Charlotte, NC (USA)
dave@sebaste.com


#19
 I have heard the same estimates for the amount of synthetic
amethyst out there. Although I must say, I'm beginning to wonder
if the figure isn't taking on a life of its own

Suzanne, somewhere I ran across some startling figures. They had to
do with the amount of cut quartz (amethyst, citrine, ametrine)
exported from Brazil, and the amount of hydrothermally-grown quartz
imported into Brazil. I’ll try to find them again for the sake of
documentation but they left no doubt in my mind that a very large
percentage of the crystalline quartzes sold are man-made.

I occasionally have business with a firm of gem cutters from Brazil.
On one visit I saw many large slabs of lab-grown quartzes of all the
above varieties waiting to be processed. Stones displayed by many
gem sellers show hundreds of amethysts with an amazing uniformity of
color, row after row of nearly identical ametrines with precise
straight lines dividing the colors, incredible colors of citrine
stones by the gross. As a cutter myself I know those qualities are
quite rare in natural material.

The public doesn’t seem to care. Price is the only thing that
counts with many people. The analogy with Gresham’s Law (bad money
drives out good) is inescapable. I remember the silver dollars that
used to jingle in my pockets when I was younger…

Rick Martin
MARTIN DESIGNS


#20

Suzanne and everybody,

I vaguely remember reading in a trade magazine or hearing on the
news around 2 years ago that QVC was going to spot check their
amethyst. I just can’t remember where I heard that

A few years ago I had a beautiful parcel of deep African Amethyst
from a trusted supplier, that I could not see any flaws. I did
send some of them to a gem lab for a verbal on them. The ones that
I sent were natural.

Then there is that problem of salting, and it is to costly to have a
lab test every stone.

I also had a request some months ago for a custom cut amethyst.
When I called my supplier who cuts in the USA, he said he did not
trust the rough and wouldn’t buy it.

This definitely hurts the industry. I would sell more amethyst if
this was not a problem. I am reluctant to have to much of it.

Diane Sadel
http://www.sweetgemstones.com