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Opalescent gems

I understand that features of the crystal that are not necessarily 'inclusions' [not involving a different substance] may also [eg. feldspar slip planes & else, calcite with polysinthetic twinning - what not! or just grain boundaries in polycrystalline 'treakle' - www , or www - famous for Raman's writing about these, or so I recall today].

Diamonds - www & www - I am not sure what works in most!
 
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I call those inclusions "particles" since I snapped up that term from a gemologist. I don't know what it is exactly. Even with magnification up to 100x Im not able to see something clear or big enough to say something about.

A very few chrysoberyl I saw on multicolor.com witch have those inside. One piece had it just in a part of the gem. Was watching through there on the homepage but didn't found it. Maybe in one or the other mixed lot chrysos there could be few chrysos witch have a bit.

From my personal experience in very light saturated colors the effect comes out the best. Well saturated colors or medium and dark tones swallow the effect.
 
Found an interesting article about it. Funny, none of mine is from Sri Lanka




Geuda is the milky corundum, formerly discarded as worthless by the Sri cutting industry that constitutes the greatest reserve of high quality heat-treatable material available. Experts believe Sri Lanka, by common consenses, has the world’s largest deposits of this particular type of corundum rough. Around 70%-80% gems mined in Sri Lanka belongs to Geuda varieties.


The term geuda itself refers to a semi-transparent to semi-translucent corundum which appears silky or milky under reflected light (normal viewing conditions), but viewed under transmitted light (the light traveling through the stone before reaching the eye) gives a characteristic ‘tea’ color known in the trade as the ‘diesel’. Both these effects are due to the presence of impurities within the crystal, that under the correct heat treatment procedures it can (if the concentrations are correct) give rise to a strong blue coloration and an increase in transparency.


Milky Or Silky Effect


This is due to the presence of inclusions of rutile (TiO²). These may be in the form of long slender needles or as clouds of minute particles.


Diesel Or Tea Effect


Iron oxide impurities give rise to brownish patches or streaks that may or may not be randomly distributed through the crystal. Sometimes the oxide patches will be oriented parallel to the crystal faces.


Local Classification Of Geuda


Over the years a considerable number of names, and a local classification have evolved. Here are a number of the most frequently used terms:


Diesel Geuda: Milky white intense brownish diesel.


Silky Geuda: Intense inclusions of rutile in the form of silk. May often display a strong diesel effect. Often further classified by its body color (yellow silky geuda)


Waxy Geuda: Material with waxy or dull appearance. May show a moderate diesel effect.


Milky Geuda: Dull white milky appearance with a diesel effect. The term blue geuda will refer to a blue milkiness with a diesel effect, while yellow geuda will indicate material with a yellowish milkiness, and so on.


Young Geuda: May be any body color, with a small amount of silk and/or diesel effect.


Thick Geuda: Opaque material with characteristic intense milkiness or diesel effect causing a dramatic reduction in transparency.


Dalan Geuda: The lowest grade of material made of mixed varieties (rejects) of geuda, usually with little silk or diesel effect. The lowest potential for successful treatment.


These coloquial names are based on the degree of concentration of the milkiness (observed under reflected light) and the intensity of the diesel effect (observed with transmitted light). The terms can be quite subjective, however, with different dealers categorizing the same materials under different names. For instance a milky geuda with a intense diesel effect may be described as diesel or milky.


Geuda was frequently stored in large drums or used to gravel home gardens prior to the 1970s discovery that heat treatment can drastically alter the stone's color. Ottu, Dun, Diesel, Milky, silky are some Geuda varieties which give blue color after heat treatments. Deguna and Red Geuda turn to red after oxidizing. Kowangu pushparaga turns to yellow sapphire after oxidizing. After heating geuda to roughly 1800 degrees Celsius, the aluminum oxide lattice-work of the gem is disrupted and cooling greatly improves both color and clarity. Though many stones are destroyed by the heating and cooling process, those that survive are significantly altered and rival naturally blue sapphires in both appearance and price.
 
I’m curious about this too. I’m not sure how to tell the difference between a silky stone and an opalescent stone. Which do you think this one would be @Lexililac ?5A22C2FE-B9EC-4612-B258-D1FF867AB386.jpeg
 
2Neezers said:
I’m curious about this too. I’m not sure how to tell the difference between a silky stone and an opalescent stone. Which do you think this one would be @Lexililac ?5A22C2FE-B9EC-4612-B258-D1FF867AB386.jpeg
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Bildschirmfoto 2020-05-23 um 20.24.38.png
That looks for me like that cloudy particles witch create that opalescent effect. This type of inclusions look different as the silk (witch are needles). If the previous article is correct its the same mineral inclusions rutile. Silk - rutile in form of needles or those clouds- rutile in form of particles.
 
Lexililac said:
Bildschirmfoto 2020-05-23 um 20.24.38.png
That looks for me like that cloudy particles witch create that opalescent effect. This type of inclusions look different as the silk (witch are needles). If the previous article is correct its the same mineral inclusions rutile. Silk - rutile in form of needles or those clouds- rutile in form of particles.
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Thanks @Lexililac ! It is such a cool effect!

@lovedogs if the pink pear interest you, I can link it here. I’m on a buying ban until I scale down what I already have.
 
2Neezers said:
Thanks @Lexililac ! It is such a cool effect!

@lovedogs if the pink pear interest you, I can link it here. I’m on a buying ban until I scale down what I already have.
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Lol I am also on a buying ban until I sell stuff. I just made a big impulse purchase, whoops! But wanted to figure out how to look for these awesome stones when my ban ends :)
 
lovedogs said:
Lol I am also on a buying ban until I sell stuff. I just made a big impulse purchase, whoops! But wanted to figure out how to look for these awesome stones when my ban ends :)
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Oh yes! I saw your gorgeous new Van Craeynest is on it’s way! Congrats!!

If anyone else is interested in the pink pear, here’s the link :

Loose gemstones, rare colored stones, pearls and certified diamonds.

Buy loose gemstones and certified diamonds direct. Choose from over 10.000 real time gemstone inventory, including alexandrite, sapphire, ruby, tanzanite, tsavorite, spinel and tourmaline.
www.multicolour.com www.multicolour.com
 
How about these? I don't know what I am looking at...

Loose gemstones, rare colored stones, pearls and certified diamonds.

Buy loose gemstones and certified diamonds direct. Choose from over 10.000 real time gemstone inventory, including alexandrite, sapphire, ruby, tanzanite, tsavorite, spinel and tourmaline.
www.multicolour.com www.multicolour.com

Loose gemstones, rare colored stones, pearls and certified diamonds.

Buy loose gemstones and certified diamonds direct. Choose from over 10.000 real time gemstone inventory, including alexandrite, sapphire, ruby, tanzanite, tsavorite, spinel and tourmaline.
www.multicolour.com www.multicolour.com
 
Dreamy!

www.leonmege.com

“811” halo with color change spinel GIA r7812

Leon Mege 811™ halo ring is made by hand and created to celebrate your majesty! Rare stone has a silky light-blue color reminiscent of the sleepy velvet of the finest Kashmir. Read full description» Set with a natural 2.50 carat Milky Blue spinel accompanied by a GIA certificate number...
www.leonmege.com www.leonmege.com


Still loving ForteKitty's ring


Sleepy Blue Spinel ring

Just realized i never posted any real life pics of this ring. 3.24ct sleepy blue spinel from Tan, approx 8x7mm, setting made by Daniel M in 14k white gold. Please excuse the extremely dry skin.. i was driving to work when i took these, and didn't have any lotion on yet!
www.pricescope.com
 
I never saw a spinel witch show that opalescent effect. Of course they can be very lovely sleepy but I think because of the single refractive way the light breaks in spinel the light never breaks in that way that this opalescent and the blue shiny effects are turning up.
 
Lexililac said:
I never saw a spinel witch show that opalescent effect. Of course they can be very lovely sleepy but I think because of the single refractive way the light breaks in spinel the light never breaks in that way that this opalescent and the blue shiny effects are turning up.
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This is good to know! Is it mostly seen in sapphire and chrysoberyl?
 
This is interesting, as for a while there, I was seeing a fair number of sapphires with this opalescent effect and always saw it as a drawback since it prevented that crystal sparkle I love. Still, they have that lovely pastel quality to them.
 
minousbijoux said:
This is interesting, as for a while there, I was seeing a fair number of sapphires with this opalescent effect and always saw it as a drawback since it prevented that crystal sparkle I love. Still, they have that lovely pastel quality to them.
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Yeah, they are a totally different look IMHO. Ethereal and glowy rather than sparkly
 
New fun hobby is window shopping for stones with this effect. Found a seller out of India who has lots of "salt and pepper" diamonds. Not my cup of tea, but also saw some really unique diamonds with this opalizing/"milky" effect. I think this is my favorite example bc its SO WEIRD (and I'm weird so think its cool).

This item is unavailable - Etsy

Find the perfect handmade gift, vintage & on-trend clothes, unique jewelry, and more… lots more.
www.etsy.com www.etsy.com

And video here:

Obviously this isn't a normal diamond so it won't have the fire, etc, but I like the ethereal look and can totally see someone like The Northway studio making it into a gorgeous unique piece.

And then there's this front greenish one that is also neat.

 
2Neezers said:
Oh yes! I saw your gorgeous new Van Craeynest is on it’s way! Congrats!!

If anyone else is interested in the pink pear, here’s the link :

Loose gemstones, rare colored stones, pearls and certified diamonds.

Buy loose gemstones and certified diamonds direct. Choose from over 10.000 real time gemstone inventory, including alexandrite, sapphire, ruby, tanzanite, tsavorite, spinel and tourmaline.
www.multicolour.com www.multicolour.com
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Did someone end up buying this?
I've been eyeing it and went to finally purchase it and it was gone :cry2:
 
TheGarnetGirl said:
Did someone end up buying this?
I've been eyeing it and went to finally purchase it and it was gone :cry2:
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Oh no :( sorry you missed it! I hope a PSer bought it so we can see pics!
 
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