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 Post subject: Heat Treated Spinel
PostPosted: Sun Aug 29, 2010 12:29 pm 
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The GIA discusses identification of heat treated natural spinel.


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 Post subject: Re: Heat Treated Spinel
PostPosted: Sun Aug 29, 2010 8:10 pm 
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NOOOOOOOOOOOO!!!!!!!!! Leave my spinels alone!!!! :evil:

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 Post subject: Re: Heat Treated Spinel
PostPosted: Sun Aug 29, 2010 11:23 pm 
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Heat treated spinels have been around for a bit now. I believe GIA sent an email out earlier in the years as well on it. I have a PDF somewhere with a whole write up on it. I will see if I can find it. I am still missing two external drives since our move, lol. :?

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 Post subject: Re: Heat Treated Spinel
PostPosted: Mon Aug 30, 2010 7:34 am 
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Thank you for the link on heat treatment of spinels Barbra.
Although aware of heat treatment of spinels, I did not realize that it was successful enough to be mainstream.
This is truly sad news for spinel lovers....

Lyric


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 Post subject: Re: Heat Treated Spinel
PostPosted: Sat Sep 04, 2010 10:29 am 
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Not to worry too much. It doesn't help the color, only clarity a little. Yet the color can be fouled if heated too high. The other big problem with heating these is that it changes the fluorescent spectral reactions in the chromium emissions. When quickly tested of the PL reactions, a heated spinel will test just like a synthetic. It's close to suicide to heat them. [-X In my opinion it would be easy enough to detect even with a hand spec. and as such would greatly devalue the stone.


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 Post subject: Re: Heat Treated Spinel
PostPosted: Fri Sep 24, 2010 7:02 pm 
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Quote:
XIX. Traitement du Spinelle :
- Violet => Jaune.
- Rouge => Rouge plus intense


source: http://www.gemmology.be/le-monde-des-gemmes/traitement

they seem to say that you can intensify the red color, or turn the purple into yellow


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 Post subject: Re: Heat Treated Spinel
PostPosted: Sat Sep 25, 2010 4:49 pm 
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I thought the entire page linked above was quite interesting.
Here is a wee translation (thru Babelfish):

Quote:
TREATMENTS OF THE INVALUABLE STONES:
TYPES OF TREATMENT:

List nonexhaustive various types of treatments.
I. Treatment by irradiation:

The stones are subjected to various rays or radiations. The change of color by irradiation is based on the principle of and the transfer colour centres of load.
Type of radiation:
- The light, the UVC and x-rays can deteriorate the color but are of relative importance.
- The gamma rays give definitely higher results: the uniformity of colouring is good and the treated stone is neither radioactive, nor hot.
The most used isotopes: Cobalt60 (Co60).
- The irradiation by bombardment with particles generates changes of color which can be stable or not, reversible or not.

(see also the notes on radiations).
II. Treatment by heating:

This technique has existed for 3000 years ACN.
Currently, the temperature can reach 2760C° to the maximum, càd the extreme point of treatment of diamond.
The crucible is out of aluminium and tolerates temperatures of 1900C°. This type of crucible is more employed because highly reliable and allows a slow penetration of heat.

New treatment beryllium boulverse since 2002 the world of the gemmeous stones. It is about a treatment by corundum heating with a beryllium supplement. See complete article on the Treatment Be.

Effect of the treatment by heating: Darkening, change of color, addition of color, cracking, reconstitution, clarification.

Detection of the treatment by heating:
a) Problem of surface.
Possibility of observing claws, wavelets, droplets of cast iron of the matter of the crucible of to the high temperature.
These defects can be attenuated by a repolishing but if they are visible, the detection of the treatment is proven.
b) Change in fluorescence UV:
Certain heated gems show a zonée reaction, blanchâtre with blue-green only under UVC. In fact especially the colourless parts have this reaction.
The yellow gems and treated oranges lose partially or completely their reaction to the UVC or UVL => Plus reaction “apricot” as in not-treated.
c) Change in solid inclusions:
During the heating, solid inclusions change volume (= Thermal Coefficient of Expansion which is single for each substance).
If it THIS of inclusion is higher than THIS gem: fracture stress in the form of halations, but attention, this case can occur in untreated stones.
Solid inclusions can also melt => vitreous residues of less volume with formation of gas bubbles taking the place of lost volume.
Other inclusions do not found but change appearance: white and round inclusions “snowball” (diagnosis 100%).
d) Change in the cavities:
When one observes gas bubbles (CO2) in a stone, one is certain that this one is not treated because CO2 disappears with the top from 31,2C°.
e) Change in the bands of color:
Blue sapphires of Sri Lanka show zones of more diffuse and turbid colors along the edges (under the microscope).
f) Change in the rutile needles:
After treatment by heating, inclusions of rutile needles “are erased” partially.
III. Other treatments:

There exist other kinds of treatments that irradiation and heating: bleaching, colourless impregnation or of color, filling, dyeing, painting of surface (=coating), joining, treatment the laser, synthetic covering, diffusion of color on the surface.
Note: many of these treatments are stable.
IV. Diffusion of color on the surface:

a) Colourless or very pale corundums are heated in a crucible of approximately 1600/1800C° and are mixed there with a powder including/understanding of aluminium, titanium or chromium as well as dyes metallic oxides (CO, Ni, V).
One thus obtains a layer of color on the surface from 0,10 to 0,40 mm (blue rubies and sapphires).

b) Heating of the stones very coloured in order to make disappear zones from colors and to distribute best.

c) Major diffusion: improvement especially of the color of the rubies.
Recognition:

* I.R. higher.
* Immersion in methylene iodide.
* Glass slightly frosted between the light and the immersed stone.
* Transmitted light.
* All the edges of the stones have larger a concentration of color.
* Side view, the stone is coloured on the surface and more or less colourless in the center (+polariscope).


V. Filling of surface:
Repair of the cracks, cavities and others reaching the surface of the stone.
One applies a silica gel in all the interstices to the surface of the stone. One heats the latter so that glass adheres and between uniformly inside.
Recognition:

* Different gloss in low-angled light.
* P.S. higher (only balances hydrostatic).
* Observation of the stone in methylene iodide.
* Gas bubbles.
* Left the stone are colourless.

VI. Dyeing and oiling.

The treatment by dyeing is only one surface treatment without diffusion (cabochon, balls, other round surfaces as well as the faceted stones).
The oiling of the stones is done by oil impregnation colourless or coloured, generally in rough stones.
Recognition:

* Friction with acetone.
* Visible oil flow.
* Visible treatment in immersion.
* Contrast under UV.

TREATMENTS BY PIERRE:

List treatments the most employed for certain stones.
I. Treatment of Corundums:
1. By irradiation:

Via bombardment with particles:
- Colourless => yellow.
- Green Blue =>
- Rose => padparadscha (orange).
This type of treatment is stable and can be reversible or not.
It is necessary to take guard with residual radiations however.
2. By heating:

By heating, change of color by destruction of the colour centre (colourless) or by change in hydration (yellow, orange).
- Silky and asterisked => transparent.
- Yellow => increases or becomes colourless.
Other possibilities:
- To develop or intensify, decrease or eliminate the component colouring in sapphire and the ruby.
- To decrease the visualization of the curved bands in the Verneuil synthesis.
- Introduction of inclusions of digital fingerprints or cracks.
- By heating + additive: diffusion of colors and/or asterism
3. Other treatments:

- Synthetic Covering.
- Dyeing.
- Filling of cracks with colourless products or colors.
- Made up Stones.
- Coating, foliage, polishing under heating.
4. Note:

- New treatment of blue sapphires “Geuda”.
Recognition: oily appearance gilded inside the stone (diesel effect) which will become blue after heating.
- Pierre Ottu. These stones only have the color surfaces some, the remainder of the stony heart being colourless.
This kind of stones takes a very beautiful yellow color or orange after heating.
- The change of color is with the replacement of Cr3+ ions by ions of Al3+ in the crystalline structure of the ruby and also of pink sapphire.
- New treatments of corundums:
Since the end of 2001, the G.I.A. is confronted with sapphires whose color was modified by heat treatment. This new type of treatment makes it possible to change corundums rosâtres coming from Madagascar as of green sapphires of out of sapphires of color “padparascha Thought”.
For the history, treatment, inclusions or how to recognize this treatment consult our article on
Treatment Be.
II. Treatments of Amber and the Ivory:
1. By heating:

With the treatment by heating, one obtains an ageing of amber and ivory. The color obscured by a light heating and/or oxidation. The ivory can also be painted in order to imitate ageing.
One also obtains the bleaching of the ivory by cleaning with bleach.
Especially for amber, one obtains, by heating, a darkening or a bleaching of the color, or of the cracks “suns”.
Moreover, it is possible to reconstitute, reassemble pieces of amber via coupled heating of pressure.
III. Treatments of Andalusite:
1. By heating:

Pink andalusite green-olive =>.
Colourless andalusite brown =>.
IV. Treatments of the coral:

The treatments of the coral most usually used are the following ones:
- Dyeing in order to make redder or orange skin; to blacken.
- Coating/Filling.
- Moulding.
V. Treatments of Beryls:
1. By irradiations:

Via bombardment with particle,
- Yellow Goshénite =>.
- Pale Héliodore green => pale or constant aquamarine.
- Emerald => emerald more marked green.
Via irradiation, one adds color,
- Addition of yellow: Green blue =>
Colourless => yellow.
Rose orange =>.
- Addition of pink: Improvement of the color of Morganite.
- Addition of blue: Colourless => blue maxixe.
Green yellow => aqua.
2. By heating:

By heating one obtains a change of color,
- Yellow => Vert, blue, colourless.
- Orange => Rose.
- Rose => Incolore.
- Blue maxixe => Incolore.
- Green => Jaune.
- By overheating, one prepares the stone for a treatment by dyeing by creating cracks, cracks.
- Covering synthetic (for beryls and emeralds).
- Dyeing (for beryls and emeralds).
- Filling: wax, oil, resin, colourless or coloured polymer (especially emerald).
- coating and foliage.
3. Treatments specific to emerald.

The aspect and the color of emerald are improved by oiling and filling of the cracks until in-depth.
Recognition:
- Flashes of color yellow, purple, green dark, blue in low-angled light and/or darkfield.
- Waxy Aspect.
- Flow of the product employed.
- With cleaning, the stone becomes milky because the product is evacuated.
The majority of emeralds are more or less treated.
VI. Treatment of Diamond:
1. By irradiation:

Via bombardment with particles,
Colourless => Noir, blue, green, yellow, brown, pink diamond or red following the nature of the particles and the intensity of the bombardment.
This treatment is stable or unstable and is reversible.
2. By heating:

Modification of the color after irradiation.
New treatment GEPOL by heating + pressure in order to improve the degree of color and purity.
Recognition of diamond GEPOL:
- Inscription of “GEPOL” to the laser on the rondist.
- Brownish Traces.
- Tiny halations of tension.
3. Filling:

Certain diamonds are clogged with glass. This treatment is called “Yehuda Treatment”.
Diamonds are heated with 400C° in order to inject there under low pressure of glass containing bismuthé lead oxychloride.
This treatment is not stable because it disappears during an important heating (ex: repair of the crimped jewel) or during a cleaning in HCl.
Recognition: Flash of color in the stone in low-angled light with fiberoptic.
4. Synthetic covering:

There exist 3 kinds of covering by a synthetic diamond film.
a) Individual Hook Films: In order to increase the P.S.
If the film is > 5 microns, the stone of comes polycrystalline, the film becomes visible because granulous and coloured.
b) Polycrystalline Diamonds Films: In order to increase the P.S.
If the film is > 5 microns, the stone of comes polycrystalline, the film becomes visible because granulous and coloured.
c) Diamond Like Carbon Films: (DLC)
In fact, it is a carbohydrate film. Hardness varies between 7&9.
The color of film can be black, gray, brown or colourless.
If film DLC is > 5 microns, the stone will react positively to the thermal driver but the film will be visible under the magnifying glass.
Application of treatment DLC on: beryls, quartz, tourmalines, garnets, titanate of strontium and on zirconium oxide.
d) Treatment the laser:
S The treatment the laser makes it possible to eliminate black inclusions in the stone. This type of treatment is easily observable.

See also the Gemmologiques News on the treatments of diamonds
VII. Treatments of Feldspars:

The treatment by heating improves the optical effect of Pierre de Lune and decreases the color in Amazonite.
The treatment by irradiation restores the color in Amazonite, Samidine or others still.
VIII. Treatments of Fluorite:

The treatment by heating decreases the blue color in the dark fluorite. The irradiation restores the color of it.
The fluorite can also be clogged.
IX. Treatments of Garnet Grossularite:

Garnet grossularite solid mass can be painted in order to imitate jadeite.
X. Treatments of Jade:

- Heating for ageing (faded the green/darker honey and brown).
- Irradiation to make the colors darker.
- Dyeing, colourless or coloured impregnation, coating.
Recognition: Microscope and with difficulty the spectroscope.
XI. Treatments of the Lapis lazuli:

The dyeing with anilines is employed but the lapis lazuli can also be tinted by wax, oil,…
Recognition: friction with a rag soaked with acetone/Test of the heated needle.
XII. Treatments of the Marbles, càd all Carbonates.

The treatment principal resides in all kinds of dyeings.
Examples: Serpentine dyed to imitate jade.
Calcite dyed to imitate turquoise.
Magnesite dyed to imitate the lapis lazuli.
Recognition: Under the microscope or the heated needle.
XIII. Treatments of Quartz:
1. By irradiation:

Via bombardment with particles,
- Rock crystal => smoked out quartz (stable and reversible treatment).
- Yellow Quartz or green => amethyst.
- Colourless Quartz => pink quartz.
2. By heating:

- Pale Quartz amethyst => yellow (citrine), green (prasiolite).
- By overheating quartz citrine amethyst last is transformed in its turn into Pierre de Lune.
- Quartz smoked => yellow-green or colourless (rock crystal).
- Chalcedony pale color => brown or red.
- Milky Quartz => Pierre de Lune
- Yellow Quartz or orange => red brown with red.
- Pink Quartz or colourless blue => (rock crystal).
3. Other treatments:

- Bleaching.
- Impregnation of colors (black onyx, Swiss lapis lazuli, chrysoprase, cornaline, jadeite,…).
- Dyeing: agates, amazonites, turquoises, malachites, chrysocolla,…
- Coating and foliage.
- Made up Stones.
- Additions of inclusions.
Often the heating intervenes after irradiation in order to stabilize the color obtained by the first treatment or to perfect this color.
XIV. Treatments of Chrysocolla.

Generally, chrysocolla is tinted in order to imitate turquoise.
XV. Treatments of Topazes:
1. By irradiation:

Via bombardment with particles,
- colourless => blue pale, brown or green
This treatment is stable and to be reversible little or not.
Recognition: Brown man exposed to atomic radiation: Too low I.R. & P.S./Blue man exposed to atomic radiation: the color obtained by irradiation is not at all the same one as natural blue topaz/Petites cracks in the shapes of celandines blanchâtres.
2. By heating:

Via heating, there is destruction of the colour centre,
- Blue or brown => Incolore.
- Orange or brown => Rosissement of the color.
Recognition: red pink/: - Fluorescence + pronounced in red.
- Dichroism + important.
XVI. Treatments of Tourmalines:
1. By irradiation:

Via bombardments with particles,
- Colourless => Pâle with red.
- Blue => Violet.
This type of treatment is stable, reversible but nondetectable with our means. It accentuates the red or the green and is often followed by a heating to 400 or 500C°.
XVII. Treatments of Apatite:
1. By heating:

- Dark Green => Green-blue, pale or colourless blue.
2. By irradiation:

- Purple => Vert.
XVIII. Treatments of the Opal:

- Treatment water for réhydrater the opal (treatment of maintenance).
- Dyeings of all kinds: to intensify the colors, noircire the opal is the most used treatment.
- Impregnation.
- Doublets and triplets or reconstituted opals
Recognition of the last type of treatments: I.R. & P.S. different from the natural opal/Microscope/Test of the heated needle.
XIX. Treatment of Spinel:

- Purple => Jaune.
- Red => more intense Rouge.
XX. Treatment of Spodumene:
1. By irradiation:

- Rose => Brun or yellow.
- Colourless or pale => Orange, yellow, green, pink.
- Purple pink, purple clearly => Yellow-green, yellow.
2. By heating:

- Brown => Vert.
- Green, purple, pink => Pâle or colourless.
XXI. Treatments of Turquoise:

Turquoise is without any doubt the most adulterated and imitated stone stones decorative.
- Various Impregnations and multiples considering the great porosity of turquoise.
- Blue Dyeing of turquoise, the matrix being dyed in black or brown.
- Colourless Impregnation known as “of stabilization”.
- Turquoise is often imitated by natural substitutes tinted or not like: chalcedony, stone of Eïlat, howlite, variscite, the amazonite,…
XXII. Treatments of Zircon:
1. By irradiation:

Via bombardment with particles,
- Colourless => pale or brown, then red.
High zircons become low or métamictes.
2. By heating:

With this process, there is destruction of the colour centre, zircon thus becomes colourless.
Low zircon or métamicte becomes normal or high.
- Brown => can take quasi all the colors.
In ceratins zircons, there is production of the cats eye effect.
XXIII. Treatments of Tanzanite:

Tanzanite brown or green takes the color blue sapphire.
XXIV. Treatments of the Pearl:
1. By irradiations:

Via bombardment with particles, the dark pearls become gray, brown, black or bluish.
This treatment is stable.


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 Post subject: Re: Heat Treated Spinel
PostPosted: Mon Sep 27, 2010 8:51 pm 
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Posts: 3170
wow, there's some surprising info from ms. b's post on treatments. here's a strange one:
"IX. Treatments of Garnet Grossularite:
Garnet grossularite solid mass can be painted in order to imitate jadeite."

:?:

and discovered a couple of weeks ago that j*v has a couple of heat treated brazilian andalusite on their website. :(


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 Post subject: Re: Heat Treated Spinel
PostPosted: Mon Sep 27, 2010 11:22 pm 
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Posts: 1246
actually massive grossular/hydrogrossular might be passed for jade without any dyeing...but maybe they dye it green when it's not.

concerning andalusite, the original text is:

Quote:
Andalusite treatments:

By heating:
Olive green andalusite => pink
Brown andalusite => colorless



(which doesn't meant there can't be any natural untreated pink or colorless andalusite)


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