Chicken Kunzite

[LD]

toothpaste!
I kid you not.

I'll give it a try! Thank you! I guess if I can cook Kunzite then toothpaste on gold should be a breeze!

 

[chrono]

LD,
I actually like the darker colour of your gold ring - it looks richer without appearing black. Oh, as for repeated heating, I also wonder if it would make the stone more brittle?

 

[Pandora II]

LD - looks like an almost identical result. Perceptible even without a reference stone IRL, and in photos.

I also love the new gold colour!

 

[KaeKae]

OMG. I just read through this thread with facination! I saw something about 'cooking' czs not too long ago, to help them achieve a nicer color, but never considered trying it on colored gemstones. I think the change is more pronounced (though still subtle, ifthat makes sense) on the natural stones. I'm wondering about a certain light amethyst I own.

LovingDiamonds: To me, the change in gold makes it look more like 18K vs 14K. Is that the case, or is it just my screen?

 

[TravelingGal]

I like the color of the new gold too! And this was a fun and informative thread...thanks for sharing all.

 

[RockHugger]

Very cool! I have a pale pink act kunzite I may heat in my x mas turkey! See if life can be breathed back into it.

 

[minousbijoux]

Anybody up for a gem saute or a good flambe (sorry I can't add the accents)?

 

[rosetta]

Dang, you have a linear accelerator at work?! Can I come to work with you?

not one, we have eight of them!

(radiotherapy department, not a secret nuclear bunker)

 

[VapidLapid]

Dang, you have a linear accelerator at work?! Can I come to work with you?

not one, we have eight of them!

(radiotherapy department, not a secret nuclear bunker)

Ha!!

For me radiotherapy is streaming wfmu

 

[Lovinggems]

This is strangely fascinating, I wish I have a Kunzite to cook with. What other gems will work with the roast chicken method?

 

[Alnitak]

Well, I'm new to the forum but I'm very knowledgeable about gemstones and kunzite in particular. Not to rain on the parade here, but I don't see any improvement--and I shouldn't. In fact, heating kunzite actually will almost always *lighten* it, not darken it. In addition, a temperature of 200C was not nearly enough to have any real impact.

Kunzite that has been treated to darken it is irradiated with an ionizing gamma radiation source, typically a cobalt-60-based device. This changes the Manganese Mn+2 to Mn+3 and Mn+4. If most of the Mn is transformed to Mn+4 the color will typically shift to a dark blue-green after this. They may also turn a brighter green similar to hiddenite, although the hiddenite color source is Chromium ions. Generally a light heating or a few hours of exposure to ultraviolet light--such as sunlight--will turn them purple. In some cases they will go back to a faint pink pretty rapidly. Some of the green crystals will literally fade in front of your eyes when exposed to sunlight.

The chemistry is somewhat more complex than this, so its not clear why some stones fade while others seem to have persistent color. In general, stones that have been treated are the ones that are most likely to rapidly fade back to light pink or even almost colorless. The process can happen without exposure to sunlight as the Mn ions will gradually decay back to Mn+2 from the Mn+3 state. This is why kunzite that is naturally dark in color is the most resistant to fading--if it hasn't faded in the millions of years since it was created in the earth, even UV exposure will not accelerate the process too much.

 

[chrono]

My understanding is that irradiated kunzite will fade rapidly when heated, even if lightly heated and only regain their colouration when irradiated, followed by heating. Is it possible that non-irradiated kunzite behaves differently? Low heat of between 100 to 200 degrees C removes the blue and purple component of kunzite, leaving it a purer pink.

 

[Alnitak]

The color is a function of the concentrations of Mn ions and a few other ions in the crystals. The color is actually naturally created by radiation in the earth, exactly the same way treating does it. The difference is that crystals that have a relatively low concentration of Mn will fade pretty rapidly whether through heating or exposure to UV. That's not a function of treating per se, just a natural result of the chemistry of the crystal. What that means is that a treated vs. untreated crystal will have no difference in fading. The reason untreated crystals seem to fade more slowly is that they are more saturated with Mn ions and the process of all of those ions decaying to lower energy states takes much, much longer. Hope this makes sense.

 

[LD]

Well, I conducted one of the experiments and I can tell you that the Kunzite did indeed darken fractionally. Whether you accept that or not, it did. I have no reason to say it did when it didn't and there was no financial value to doing this - in fact the stone could have cracked and I would have been left with smithereens! Of course, it's difficult to judge when the change is subtle and it could also have reflected the darkening of the metal BUT both Pandora (who is a gemmologist) and I achieved the same results.

 

[Alnitak]

Well, I conducted one of the experiments and I can tell you that the Kunzite did indeed darken fractionally. Whether you accept that or not, it did. I have no reason to say it did when it didn't and there was no financial value to doing this - in fact the stone could have cracked and I would have been left with smithereens! Of course, it's difficult to judge when the change is subtle and it could also have reflected the darkening of the metal BUT both Pandora (who is a gemmologist) and I achieved the same results.

The problem is that our eyes can fool us, especially when we are expecting a result. In the case of your ring, I personally couldn't see a difference in the photos and its likely any difference is due to the darkening of the ring. With the other stone, when I place the two images beside each other and normalize the exposure and contrast, they also look identical. The picture next to the color chart is deceptive to the eyes because in the "before" shot we're looking down through the side of the stone. Not only does this window and therefore show lighter color, but kunzite is also strongly pleochroic, so looking at it from different angles can change the color and intensity of the color.

The science of the color and how it changes is pretty clear. No matter what we want to think or see, the science doesn't change. Light heating of kunzite is occasionally used in the trade to try and clear up greenish or bluish tones to get a more pure pink. This is done at the 150-200C range, just like what you did. That simply won't and can't darken the purple/pink--its not possible due to the chemical composition of the crystal.

Let me give a little scientific lesson on color in crystals. I think it will help. Colors in most gemstones comes from the positioning of small number of elemental ions in certain crystallographic sites--these are typically called "color centers." If you took high school chemistry and/or physics you may recall learning about electron orbitals. The first-row transition elements (Titanium, Vanadium, Chromium, Manganese, Iron, Cobalt, Nickel and Copper) all have five 3d orbitals which allow for various oxidation states of these elements. It's these oxidation states that cause the colors we see when we look at a gemstone--natural light excites an ion from one state to another, and as the transition occurs, light of a certain wavelength or wavelengths is subtracted from the incident light, causing us to see the color. Thus chromium and vanadium can cause green in beryl, making emerald, while iron in beryl makes blue aquamarine. Different states of the same element can cause different colors: Iron oxidized to Fe+2 causes the blue of aquamarine, but when further oxidized to Fe+3 the color changes to the yellow and we call the beryl heliodor.

Now let's turn to kunzite. The coloration of kunzite comes from primarily manganese ions. When the manganese is mostly reduced, the coloration we see comes from Mn+2 ions in the octahedral color centers of the crystal. In nearly all crystals, Mn+2 imparts a pale pink hue. When the manganese is more highly energized, it's in the Mn+3 state. This imparts a purple hue. This is a rarer hue as it requires a larger total concentration of manganese in the crystals. The larger the concentration, the greater the concentration of Mn+3 ions in the color centers, and therefore a deeper purple. However, over time the Mn ions will gradually reduce back to a more stable Mn+2 state or a base state of Mn+0. This is why kunzite fades over time. When the Mn ions are highly oxidized they can enter the Mn+4 state. This results in a bluish-green hue. This energy state of the ions is quite unstable and they will rapidly reduce to Mn+3 upon light heating and/or exposure to UV radiation. Again, in a higher concentration of Mn will result in this process taking longer as more Mn ions are trapped in each oxidation-reduction state in the color centers in the crystals.

This whole process is called tenebrescence and it is reversible. This is the basis of treatment of many gemstones. Exposure to strong ionizing radiation will causes the transition elements to oxidize to higher energy states of the ions. Heat and UV radiation both reduce the ions to lower energy states, reversing the process. So irradiating pale blue beryl can create yellow heliodor, and heating can return it to aquamarine. Light heating can remove the yellowish overtones of the Fe+3 ions, making a more pure blue, but heated too high and for too long, and you can bleach it out to clear goshenite. In kunzite, if the manganese concentration is sufficiently high enough, irradiation will turn the crystals a deep green. Afghan kunzite is often treated this way and sold as "hiddenite." This is a false hiddenite, as true hiddenite is actually spodumene colored green from chromium, and that green is very stable as the Cr+3 ions are slow to reduce. The green from Mn+4 is not stable, as Mn+4 is easily reduced to Mn+3 and Mn+2. The Mn+4 green kunzite crystals will typically very rapidly fade to purple or pink depending on the total concentration of Mn in the crystal. In crystals with a high concentration of Mn, more ions can remain in higher oxidation states, meaning the colors can last longer.

At the Oceanview Mine in California (where I have worked helping mine kunzite), the kunzite crystals are heavily saturated with Mn. Many of them come out of the ground a deep bluish-green or a mix of bluish-green and purple. The natural radiation from the surrounding granite and some other Uranium-based minerals has oxidized the Mn to Mn+4. After 3-4 hours in the sun, the crystals will deep a very deep dark purple as the Mn is reduced to Mn+4. I've had pale blue-green kunzite from Afghanistan that changed to a pale purple in the sun, often in as little as 30 minutes. The Mn concentration in those crystals was lower, hence the lower total color saturation. I can also keep these out of the sun and heat them and get the same effect. Typically kunzite is irradiated until it turns green to ensure that the maximum amount of Mn ions have been oxidized so that the color saturation and retention are best. Its then carefully heated or exposed to controlled UV until its purple to purple-pink. That said, if the Mn concentration is too low, it may never get very dark, and it could fade very rapidly.

What does this all mean? Well, simply put it means that heating kunzite won't darken the pink/purple color, as heat will reduce Mn+4 and Mn+3 to Mn+2 and the base state--which will decrease the total color of the kunzite. Its a function of chemistry and physics. If you want to darken your kunzite after its faded, the way to do is to send it off to a lab that will irradiate it and heat it as required. Heating it at home will do nothing except potentially fracture the gem or possibly even bleach it out a bit (although the temperatures in an oven are not generally high enough to achieve much bleaching).

I know its hard to not believe our own eyes, but if I learned one thing in all of my scientific training in grad school, its that our eyes and minds can very easily trick us. Repeatability under controlled circumstances is key. In this case, the science of the core color and color change process is well understood, and its very repeatable--indeed, that science is the basis for the entire process of treating kunzite for the gem market.

 

[minousbijoux]

Alnitak: thanks so much for your posting; it (finally) explains what is happening internally in the radiation and/or simple heating processes. I don't have any kunzite for the very reason that I'd hate to watch it change over time, or to have to take action to reverse a change. But its still fascinating info.

 

[Alnitak]

Alnitak: thanks so much for your posting; it (finally) explains what is happening internally in the radiation and/or simple heating processes. I don't have any kunzite for the very reason that I'd hate to watch it change over time, or to have to take action to reverse a change. But its still fascinating info.

No problem, glad to help. I'm always leery about getting too technical or scientific...my wife tells me that it bores some people.

I wouldn't let it scare you away--if you can get one that is naturally very dark, the fade rate can be very slow. So slow that it won't seem to fade in your lifetime, especially if you use it as an evening stone. As an example, I have a piece from the Oceanview Mine that has been sitting in the sun for several hours a day, three days a week for over a year. It faded from a more purple color to a deep lilac pink. The color is still incredible--and the amount of exposure to UV it had would take a lifetime of use as an evening stone. Some Afghan and Brazilian kunzite is similarly fade-resistant, but its rarer and you will pay a lot more. Unlike cheap kunzite which can be found as low as $10-15/carat, high-grade natural deep-colored kunzite can sell for as high as $200/carat. Here's an example from the Oceanview Mine. It's 43.7 carats and a deep purple. In fluorescent lighting like I used for this photo, it's got bluish highlights; in sunlight or incandescent light its got reddish-purple highlights. Stones like this one have auctioned recently in the $200+/carat range.

 

[minousbijoux]

Wow, that is unbelievably beautiful! Now that is a color I can totally get behind.

On a completely different note, if you are in the trade, you must declare yourself as such. If you go back into the My Pages section, there is an area where you can change your status and make yourself a trade member. The moderators here are very diligent and thorough (as well they should be) at maintaining this rule. The other thing is that I would check whether your image is allowed as is. I *believe* though this might've changed recently due to image theft, that one is not allowed to have marked images such as yours. Perhaps if they are allowed, you must state that the stone is not for sale? Anyway, worth checking as we'd like to have you stick around

 

[Alnitak]

Wow, that is unbelievably beautiful! Now that is a color I can totally get behind.

On a completely different note, if you are in the trade, you must declare yourself as such. If you go back into the My Pages section, there is an area where you can change your status and make yourself a trade member. The moderators here are very diligent and thorough (as well they should be) at maintaining this rule. The other thing is that I would check whether your image is allowed as is. I *believe* though this might've changed recently due to image theft, that one is not allowed to have marked images such as yours. Perhaps if they are allowed, you must state that the stone is not for sale? Anyway, worth checking as we'd like to have you stick around

Thanks for the heads up. I understood that one wasn't allowed to shill stuff here, but I didn't think that I was required to declare the fact that I do sell. It's not my primary employment, so I don't consider myself "in the trade" but I'll go make that change regardless.

I hope they don't have a policy against watermarking images otherwise I won't be posting any. Too many images of mine stolen over the years, and a lot of time and effort goes into my photography--so it's all visibly and invisibly watermarked.

 

[chrono]

If it is your business (it does not have to be your primary occupation), you must declare your trade status. A frequent PS contributer named Gene is an engineer by day and lapidary by night. Sounds like he's a moonlighting superhero, doesn't it? He has to declare his trade status too. I think watermarks are fine but the stone pictured must be either already sold or not for sale.

 

[LD]

You might want to check about watermarks with the moderators. I thought that the rules on this changed a while ago and now all logos and anything that identifies the source had to be removed - I could be wrong but better you get it checked.

I'm going to be honest and say that I couldn't read all your post as at the moment I have the attention span of a gnat (apologies). What I will say is that in my experience I haven't been able to predict which Kunzites will fade and which won't I had one that was kept in a safe ALL the time and it was there for a couple of years without seeing daylight. I got it out and it had faded incredibly. It WAS a pretty saturated one but ended up pale and insignificant (a bit like me in the winter time!).

I've got an absolutely gorgeous pendant of decent size that is a deep colour and I am paranoid that one is going to fade - as yet it hasn't so I'm hoping it's going to be one that decides to lose its tan very very very slowly!

The one in your photo is a magnificent specimen. Really glorious. That's the holy grail of Kunzites!

 

[Alnitak]

OK, I've made the change to "Trade" now that I understand.

This stone is not being actively sold, but I'll always sell anything in my collection for the right price. Seriously, though this is a personal collection piece. If anything it might be donated some day to the Los Angeles Natural History Museum. I've been working with the guys at the Oceanview Mine in Pala, California for about six months now, having fun actually *mining* gemstones. I have a collection of pieces of natural crystals and some in cut gem form. I do also have a side business selling mineral specimens, gems and jewelry but I won't post that here, so you'll have to figure it out on your own.

OK, so I'll see what they say on the watermark, but it would be silly to block people from using their *own* watermarks, as that's some of the only protection we have for images on the Internet.

On the kunzite you have that's faded in the safe--that's no doubt one that was treated by being irradiated/heated. If you get a chance to read my long and somewhat boring post, you'll see that color saturation and retention is primarily a function of manganese content. If the percent of Mn by dry weight is relatively high, the stone will fade so slowly and imperceptibly as to appear to be fade-resistant on a human time scale. Some treated kunzites will keep a deep color for a long time as well--if a natural crystal was subjected to heat in the ground, it can be pale even with a large concentration of manganese. Alternatively, it may have never gotten large enough doses of natural radiation for it to turn purple or dark pink. Not all pegmatites have radioactive minerals in them and/or the surrounding country rock that the pegmatite intruded into may be insufficiently radioactive to have darkened up the crystals. In addition, some pegmatites like the ones in Afghanistan are relatively "young" in geologic terms, so the crystals have not had enough time in the ground to receive the natural radiation doses that would darken them up.

In that sense, the treatment really is just an accelerated version of the natural processes that create these colored crystals. The unnatural part is that we give it a huge dose of the radiation very rapidly, so we might get a great color, but it won't last because the Mn content just isn't high enough.

Generally speaking if you have a kunzite that hasn't faded after about 3-5 years, it will remain relatively fade-resistant. It's still always best to keep it out of direct sun and away from heat, as those will speed up fading no matter what--but a good rich-colored kunzite will be safer to wear without fear of fading if its remained stable for some time. I could show you a picture of a stone that's been in the sun for 3 days a week for over a year and it has retained a rich lilac color, but its for sale elsewhere on the Internet, so apparently I can't share that image. A bit of a lame rule, because the forums will miss out on a lot of great stones. Seems to me that as long as your aren't trying to sell it here it wouldn't matter. Anyway....

 

[LD]

I don't disagree about the rules but those are the rules! We have a high number of vendors who post on here and even if this is a side-line for you the rules are quite strict because you can't comment on your own stones etc etc. It may be worth reading up on them because I think they're fairly restrictive.

What is great is to have people on the forum who love gemstones, have a genuine interest in them and want to talk about them!

Thanks for the info on the Kunzites. I never venture out in daylight with them and know all the "rules" about what to do with them but it's so annoying when they fade! I didn't realise that the Afghan stones might be considered "young" and that's really interesting and makes a lot of sense.

You may have an answer to something that's puzzled me for YEARS! About 10 years ago (or something like that), I bought a 24ct Hiddenite. When it arrived it smelled strongly of petrol and felt oily. I was intringued as I'd never seen anything like that before. When I opened the parcel it was the most gorgeous green I'd seen - almost too good to be true (see below). However, within a couple of weeks this had faded to a mint green and now, all those years later, the colour is stable (well it hasn't faded any more) and now is the palest palest green - almost white with a hint of green. So, what's caused that? Irradiation but if so, why the petrol smell? Any ideas?

 

[Alnitak]

You may have an answer to something that's puzzled me for YEARS! About 10 years ago (or something like that), I bought a 24ct Hiddenite. When it arrived it smelled strongly of petrol and felt oily. I was intringued as I'd never seen anything like that before. When I opened the parcel it was the most gorgeous green I'd seen - almost too good to be true (see below). However, within a couple of weeks this had faded to a mint green and now, all those years later, the colour is stable (well it hasn't faded any more) and now is the palest palest green - almost white with a hint of green. So, what's caused that? Irradiation but if so, why the petrol smell? Any ideas?

Wow. That is a great color. Definitely not a hiddenite as the true Hiddenites from North Carolina don't fade--the Cr+ ions are too stable for that. I've heard of that oily smell and texture before. The only thing I can think of is some sort of diffusion treatment that would leave a residue. A simple irradiation of kunzite produces a different color if its predominantly colored by manganese.

I'm extremely leery of stones from Afghanistan if I can't actually buy the rough and cut it myself. Even then they are now irradiating full crystals so they can call them hiddenite and get more money for them. My concern with treatments is that they are using compounds or processes that could have adverse health effects. There was a time in the past where topaz was irradiated in nuclear reactors instead of safer sources of radiation, making the stones radioactive. That was discovered and the federal government in the US put a ban in place on stones treated that way.

I don't know exactly how these deep emerald green stones are being produced, but the common thread is that oily smell, so its something different that just a standard irradiation. Now I'm intrigued enough to figure it out....

 

[LD]

Well if you figure it out, please let me know! I don't know the origin of this stone (although if I spend some time I will probably be able to find the original documentation), so I'm not sure if this was purported to be from Afghanistan or elsewhere.

 

[Alnitak]

So here's what I'm finding on green "kunzite" which really should be called green spodumene, since kunzite is the name for the pink-purple variety of spodumene.

As some of you will know, there is a form of green spodumene called Hiddenite. It's named after William Hidden, and was discovered in North Carolina, in an area that now bears the name of the man and mineral--Hiddenite, NC. The coloration of hiddenite comes from chromium and trace amounts of vanadium--just like emerald, which is found in that same area.

In recent years some small amounts of green spodumene have been found in other localities that have Cr as the color source, and share the green color of the NC material, although generally its not as intense in color. This includes a find from Afghanistan dating to about 2005 or 2006. Unlike the treated material that is green, this material does not fade upon exposure to the sun. In addition, the Cr ions don't respond to irradiation or heating in the same fashion, so they can't be darkened or heated. This material was very rare and limited in production.

Some of the more blue Afghan material will treat to a deep green. This is the very unstable color. Even in the absence of sunlight it will fade over time. With direct exposure to UV it will convert to a pink color that is fairly pale. It appears that this material may have a higher Fe content relative to the Mn content, and this plays some role not only in the green color it attains, but also in the overall pale nature of the material when it finally fades as its a function of the Mn content and its proportion relative to iron that affect the color--the more Mn and less iron, the more purple the colors become. As the ratio of Fe and Mn change to more Fe, the color becomes more pink and then eventually yellow to colorless. The intensity of these colors is also affected by the total Mn and Fe content, and not just the ratios.

In the case of your green stone, I can't explain the petrol odor and greasy texture, but it seems that it was no doubt irradiated. Likely they skipped the heating step that would have shifted it to pink to pink-purple. Not that you would want to try this, but I suspect that if you left it in the sun for about 30 minutes it would fade out to a very pale pink to colorless.

 

[minousbijoux]

I am not LD but just want to say that I find your posts fascinating! I love the logic of the mineral components. Do you have any photos of the rare intense and stable green found elsewhere?

 

[LD]

Thank you that was great information. I had assumed that this had been irradiated which was unstable. It was the smell/texture that completely threw me and I wondered if that was a different treatment I was unaware of. This faded without exposure to any sunlight and it's been in a safe for years now and seems stable. Interestingly it hasn't gone yellow or pink but has stayed as a very very pale hint of a tint of green! When I get some time, I'll take a photograph for you to see. It's such a shame because the green was marvelous and I'd love to get that back (without the fading issue)!

 

[chrono]

Must be something used in the irradiation process that smells like petrol.

 

[Alnitak]

OK, last night I had very fortuitous and interesting meeting! I was attending my first joint annual meeting in Pasadena of the Gem & Mineral Council of the Los Angeles Natural History Museum and the Mineralogical Society of Southern California. By pure chance, I sat next to Dr. George Rossman from CalTech. He's a mineralogy professor and one of his areas of focus is the coloration of minerals by elemantal cations. In fact, he's been looking at spodumene...wow! We had an engaging conversation and I'm going to be heading over to his lab with some samples from the Oceanview Mine and other nearby mines for some analysis.

Anyway, back to the other items. The more pure green of spodumene colored by chromium and called Hiddenite can be seen here:

http://geogallery.si.edu/index.php/en/10266184/spodumene-with-hiddenite

I'm a bit confused about the rules for posting links here, but I most certainly will NOT copy their image and post it here. It seems to me that it should be fine to post a link to the Smithsonian Institution, but again, the rules on links here are not clear on this. While I'm at it, here's a link to the Gemological Institute of America's article on the green chromium-colored spodumene (so yes, its true hiddenite) from Afghanistan:

http://www.gia.edu/research-resources/gems-gemology/issues/fall2007-contents/fall2007-featured-gemnewsintl.html

Now, the bulk of the green material coming from Afghanistan is treated, and the green comes from Manganese in crystals with a very low iron content. It will give them a very clean green color, but it does fade and when exposed to UV will rapidly turn either pink or colorless. This was confirmed by Dr. Rossman last night. I also spoke with a friend from Brazil who gets pale Afghan kunzite treated, and he confirmed that it comes back from the Cobalt-60 irradiation process a beautiful green. It's then heated to turn it pink; its apparently a bit more stable when heated than just exposed to UV, but it can fade and most does--it's just the rate at which it fades that varies.