Is there a way to tell the difference between heated zoisite and
real tanzinite? I have invested some money in a lot of tanzinite and
now wondering if any is a heated zoisite, since I have come across
some people who color the discriptions in the past.
All blue tanzanite is heated
Not true Tanzanite does fade light as does amethyst, and other
stones with some calcium in them Regardless of what any dated
publications prior to the 2007 announcements put out by the AGTA and
other gem trade associations world wide universally they have arived
at standards regarding saturation, hues and grading and in none of
the material regarding natural tanzanite does it mention that the top
grade material is heated or otherwise treated. Real tanzanite is
untreated and ranges from bluish purple to purplish blue and in about
5 hues related to those tones. the material is graded A-AAA, AAA
being the finest. Regarding care, it should not be left in sunlight,
cleaned in an ultrasonic cleaner, nor steam cleaned (what’s left!)…
anyway that’s what the AGTA literature says.
Hi Folks…
Is there a way to tell the difference between heated zoisite and real tanzinite? I have invested some money in a lot of tanzinite and now wondering if any is a heated zoisite, since I have come across some people who color the discriptions in the past.
Last I heard, Tanzanite is always heated…
Not that Ma Nature could not accomplish the job…
But that’s just the way it is…
If I’m wrong, please let me know…
Gary W. Bourbonais
L’Hermite Aromatique
A.J.P. (GIA)
*Not true* *Tanzanite does fade light* as does amethyst, and other stones with some calcium in them Regardless of what any dated publications prior to the 2007 announcements put out by the AGTA and other gem trade associations world wide
I have 3 questions.
-
What is the source of your ?
-
Can you describe the process causing Tanzanite to fade ?
-
Why are you singling out calcium as an admixture responsible for
gemstones instability in the sunlight ?
In gemology we always say that things are true until they change.
Your statement is contradictory to the that I have ( you
right about amethyst fading, but not the cause for it ). Did I miss
something that was released recently ?
Leonid Surpin
Hematite is is an oxide of iron (Fe3O2) and it is possible it could
leave some red on the skin.
Malachite is a dicopper carbonate dihydroxide ( OC(OCuOH)2 ) with no
iron present. Copper normally leaves green on the skin.
I must assume that it is possible that both hematite or malachite
might leave color on the skin, but I’ve never heard of such being a
problem with most people.
A good quick source for chemical is wolframalpha.com. I
searched for both the minerals above at that site. I’m no chemist.
Mike DeBurgh, GJG
Henderson, NV
This conversation is starting to sound to me like there are two
types of tanzanite ? Obviously some have experience with fading
tanzanite while others have experience with tanzanite thate does not
fade. perhaps some of this tanzanite is treated in a manner that does
not last or, it is not tanzanite at all … not trying to insult
anyone here but this is the picture of what the content of the thread
is is painting tanzanite either does or does not fade in sunlight.
The evidence of testimony so far would suggest that if a number of
people are having dis-similar experience then the most likely
possibility is somebody out there is selling somthing that is fake or
the treatment on the stone is inferior
goo
You have a lot more faith in retail jewelers' omniscience and infallibility than I do
Not infallible Al - experienced.
Since it might kill a sale, it seems they would NOT mention it in
their web ads if they didn’t believe it could possibly happen.
Ray Gabriel
Gabriel Gems - www.raygabriel.com
1. What is the source of your ?
- AGTA ( as I said in the post), IGTA etc. I also have a friend in
Tanzania that mines tanzanite, tsavorite and other stones near the
Mt. tsavo national Park East side- he is very knowledgeable about
his products and keeps up with the latest publications that he sends
me ( along with rough!) regularly regarding grading, standardisation,
etc.
2. Can you describe the process causing Tanzanite to fade ?
- sunlight- like leaving stones in a gem jar in the sun on a shelf,
or otherwise exposed to bright light
3. Why are you singling out calcium as an admixture responsible for gemstones instability in the sunlight ?
- calcium containing stones seem to fade faster than stones without
it, same is true for lithium ore stones and kunzite, morganite,
kyanite, lepidolite etc. the calcium content assists their fading
when expose to sunlight for long periods (like leaving it on a shelf
in a display case etc. near a window There’s a lot of info on the web
that says it is all treated it is not, it depends on whether or not
you believe everything you read… perhaps the gems that the author of
x article is familiar with are treated as it does happen but it is
not the rule or universally practised…by every dealer seller and
miner everywhere always…that’s my point…it is not always done by
everyone selling the stone.
Well, you and others who have posted on this forum are wrong on some facts concerning tanzanite.
The color is not brought about by heating.
The material is pleochroic in it’s natural form; oriented in a
certain way it is orange.
Heating is done to enhance the color; but the material zoisite is,
or may be. blue in color in its natural state.
Tanzanite is a marketing name given to this material.
I have a 7+ caret, square brilliant stone which I faceted from
unheated material.
It is a lovely blue color. I cut some smaller stones from the same
piece of rough.
I heated a couple of those to see the effect. I wasn’t able to see
any great difference in color.
I believe the material that is heated after faceting is more of a
gray/violet color and is an attempt to bring out the blue color.
I still have the square brilliant.
I don’t know whether it’s possible (if there’s a test) to tell if a
stone is heated.
KPK
Since I can't believe retail jewelers would mention the fading if it were not real,
Having worked in a retail mall jewelry store I’ll have to admit I
have less than perfect confidence in everything I’m told by some
(not all by any means) retail jewelers. I guess it probably doesn’t
help when I’ve been told “Oh no” virtually every time when I ask if
something has been treated or is genuine.
Mike DeBurgh, GJG
Henderson, NV
Since it might kill a sale, it seems they would NOT mention it in their web ads if they didn't believe it could possibly happen.
Then what about the majority who say it doesn’t happen, or don’t
publish such a warning? I suspect that some are just repeating
from a source no more reliable than this thread.
Or their lawyers heard a rumor and are in CYA mode.
Al Balmer
Sun City, AZ
*Not true* *Tanzanite does fade light*... anyway that's what the AGTA literature says.
Do you have a AGTA reference that’s available to the public?
Al Balmer
Sun City, AZ
Since it might kill a sale, it seems they would NOT mention it in their web ads if they didn't believe it could possibly happen.
Or, in this age of litigation over anything, they might mention it
even if not sure, just to avoid being accused of not warning people
in the event that it does happen somehow, even if they are not sure
that it does, or where they heard the rumor. I know some jewelers,
for example, who simply tell customers that so far as they know,
almost all gems are treated. They don’t know whether a certain one
is or not, they just assume it is. Now, this means they’re telling
people that some stones where are not treated, might be. Even some
varieties which are never treated, fall under this umbrella simply
because the jeweler is being cautious. No doubt they loose a few
sales with this, but they feel safer from accusations of
misrepresentation. These folks contrast nicely with the few jewelers
out there who make claims like “the stones other jewelers sell might
be treated, but ours never are…”
Peter
Regardless of what any dated publications prior to the 2007 announcements put out by the AGTA and other gem trade associations world wide universally they have arived at standards regarding saturation, hues and grading and in none of the material regarding natural tanzanite does it mention that the top grade material is heated or otherwise treated. Real tanzanite is untreated
Sigh.
With all due respect, please do a bit more research.
Tanzanite, as it comes out of the ground at every mine I’ve ever
heard about, at least according to the miners I’ve heard, including
the late Cambell Bridges when he talked about it at a Tucson show
many years ago, is not purple.
Tanzanite is trichroic. One of the three colors is a nice blue,
another a reddish tone, and the third is a rather brownish yellow.
All this makes tanzanite a rather unique material optically. But the
combined three colors mean the mined material is brownish. Heating
the stone bleaches (?) the brown/yellow to an almost clear color. You
see these colors, either in the original untreated material, or after
treatment, with a polariscope best, by the way.
In order to get the attractive purple/blue colors, heat treatment is
essential. It doesn’t occur without the heat treatment, except if
there were some rare situation where a stone was sufficiently heated
in nature. Perhaps sitting in the african sun somehow it could reach
the required several hundred degree temperature? But nobody I’ve ever
talked to (miners or gem dealers) has ever seen one they could attest
was naturally heated. The natural geology of the gems formation does
not do it. All of them are heated, very carefully, after mining.
Without it, the purple color is not visible, being totally masked by
the strong brownish yellow pleochroic direction. Once that is
removed by heating, the blue and reddish pleochroic colors combine in
various ways depending on how the stone is oriented and cut, to give
the blue to purple color range we associate with Tanzanite.
If AGTA or other sources don’t make much mention of heat treatment,
it may simply be due to the fact that it’s assumed the people know
that this treatment is an essential part of the cutting and
processing of this material. You simply don’t find it any other way.
And to the poster who said:
Is there a way to tell the difference between heated zoisite and real tanzinite? I have invested some money in a lot of tanzinite and now wondering if any is a heated zoisite, since I have come across some people who color the discriptions in the past.
In short, heated zoisite IS real tanzanite, IF it then displays the
nice blue to purple color. Ordinary/common green zoisite, heat
treated, does NOT turn blue/purple. Either way, the gem is a color
variety of the mineral zoisite. it’s unique in that it DOES turn
blue/purple when heated properly. If what you purchased is indeed
tanzanite, then by definition, it is a variety of zoisite that has
been heat treated to give the desired final color.
The only other option would be a simulated tanzanite. There are some
simulants on the market that are not zoisite, nor tanzanite, nor any
other natural stone, so far as I know, but which are made with a nice
blue color, and sometimes fraudulently sold as tanzanite, or
legitimately sold as a simulated tanzanite substitute. That stuff is
generally very cheap. I don’t recall, unfortunately, exactly what the
material is made of… Some synthetic or other, or maybe a glass.
Don’t know. Tanzanite itself (heat treated blue/purple zoisite) has
not, to my knowlege, yet been synthesized.
Peter Rowe G.G.
or while were arguing over how tanzanite is sensitive to heat, if its
sudden or whatever someones ten year old is taking a hammer to a
diamond because its hard… toughness… hardness… just take the
hammer.
Hello Debra,
I regret to tell you that all tanzanite is just a variety of zoisite
that has undergone heat treatment at around 500degC
Fernando F. Escudero
Regards.
Care and Cleaning
Tanzanite should be cleaned using warm, soapy water. Ultrasonic
cleaners and steam cleaners should never be used.
Tanzanite is special-care gem for two reasons: sensitivity to
thermal shock and the potential for cleavage. Sometimes the
temperature change between the hot lights of the display case and the
chilly glass countertop in an air-conditioned showroom can be enough
to develop cleavages in tanzanite. This is from GIAs Gem Reference
Guide 1999.
When I say “cant take heat” its Bench Jeweler lingo as in not
diamond, ruby, etc. not every employee is going to be a G.G.,
expierience takes time, so we make the rules and explain later. So
be careful with the Tanzanite… It cant take heat.
I regret to tell you that all tanzanite is just a variety of zoisite that has undergone heat treatment at around 500degC
Yes. But regrets probably aren’t needed. Tanzanite, though a variety
of Zoisite, is a much rarer variety than the usual forms of zoisite
seen (the massive green stuff…) And quite a bit more valuable than
other varieties…
Peter Rowe
I have a 7+ caret, square brilliant stone which I faceted from unheated material. It is a lovely blue color. I cut some smaller stones from the same piece of rough.
Kevin, did you dig it out of the ground yourself? If not, assume the
stone, like most rough, was already heat treated properly when you
bought it. So far as I know, most of the heat treatment of tanzanite
is done by the miners or soon after. among other things, the final
color cannot be accurately judged till after treatment, so they
don’t know exactly what to charge till they know what they have. At
least, that’s my understanding of the situation.
Peter Rowe
Regardless of what any dated publications prior to the 2007 announcements put out by the AGTA and other gem trade associations world wide universally they have arived at standards regarding saturation, hues and grading and in none of the material regarding natural tanzanite does it mention that the top grade material is heated or otherwise treated. Real tanzanite is untreated
From the AGTA website
http://www.agta.org/gemstones/variation-tanzanite.html
“Virtually every tanzanite is heated to permanently change its color
from orange-brown to the spectacular violet-blue color for which this
precious gemstone variety is known.”
Beth