Irradiated and natural smoky quartz

Is there any way to distinguish irradiated from natural smoky quartz , especially of there is no matrix ? One source says that the presence of phantoms indicates that the color is natural. Is this true?

Hi Howard,

You can try to heat it a bit, if it goes colorless or becomes lighter, chances are very good it has been irradiated. Don't heat it to quickly or intensely, the quartz will crack or even "pop" (wear safety glasses). Also the irradiated quartz crystals will be smoky and the main body of quartz matrix will remain unchanged on irradiated specimens. There is a good paper I read some time ago on this topic, referenced below.

Ref.

[www.scielo.br]

Hi again Howard,

Just a quick word of caution. If this is a specimen that you like and enjoy the way it is, don't heat it. It will likely change or even become damaged by the heating process. Try the visual inspection method first. If the smoky quartz crystal has some quartz matrix in association maybe some of it is opaque or white in color, these areas will not generally darken due to the irradiation process. Therefore if these areas are not smoky, the specimen has likely been irradiated.

Ron

Note that natural smoky Quartz is coloured due to lattice defects. It too will fade/change when heated. This is not a distinguishing feature between natural and irradiated Quartz.


All the best

Claus

____________________________________________________________________________
Claus Hedegaard
Google me to find me!



Edited 1 time(s). Last edit at 02/15/2009 09:47PM by Claus Hedegaard.

Hi Claus,

Thank you for correcting my obivious misstatement. I don't know what I was thinking when I wrote the first post, I do know differently, even from the practical experience of having personally heated both irradited rock crystal and naturally smoky quartz many times, as well as understanding the mechanics and chemistry involved! I guess I was in a rush to give bit of helpful advise without thinking it through properly (mental lapse). I've reread my first post several times and am still confounded why I even wrote it. My sincere apologies to Howard and anyone else I confused with that post. I will call this my first senior moment, have a good laugh at myself and endeavour to proofread more carefully before I rush to help again. Thanks again Claus.:)

Ron

Howard,

I've read in some article that it is possible to distinguish natural and artificially irradiated smoky quartz, but you would need laboratory equipment to do this.

Radiation leaves traces in the crystal's substance. In some minerals (I remember apatite) these "scars" look like short hollow tubes (although I'm not sure that these are real tubes, it might just be material with different optical properties, because it turned amorphous, for example).
Natural radiation has a wide energy spectrum and comes from many different directions.
Artificial irradiation is aimed at the crystal and has a very narrow energy band.
My guess is that this causes differences in the pattern of the traces.
(I think I should dig out that article and finally contact these people and aks them how they do it...)

But there are no other means to tell, except for experience. You know an irradiated Arkansas quartz once someone showed you one, they just have a certain look, and that's all.

Phantoms or color zones are not helpful either. The color in smoky quartz develops long after the crystal growth stopped. The color centers are temperature sensitive, and if you are very patient you could pale a smoky quartz at rather low temperatures, like 100deg C (that will probably take many years, though). So under the hydrothermal conditions at which the crystals grow color centers are unstable. They only remain smoky after the crystal is "done" when the temperature dropped below about 50-60 deg C.
The color zones are there because the relative contents of trace elements (aluminum plus either hydrogen, lithium or sodium) in the crystal lattice change during growth. So you'd expect to see phantoms in artificially irradiated rock crystals as well.

Sometimes one sees strange changes in the color patterns of smoky crystals that have been heated (paled) and subsequently irradiated. The natural smoky zones will simply turn dark again and look the same as before, but some of those parts of the crystal that were colorless in the natural condition turn almost black upon irradiation. This might be an indication that some parts of the crystals develop color centers that are less stable and that are easier to pale.

But even if this was true, you cannot really say something like "natural color centers are stable up to this temperature", so I wouldn't draw any conclusions from the fact that some specimens can be paled more easily.

Amir

It's really easy to tell the natural smoky quartz from artificially irradiated smoky quartz: Just ask a mystical collector to hold it and ask them whether they detect healing vibrations or evil vibrations! (Sorry, just kidding.)

Actually, I once met someone once who claimed to be able to do that. She closed her shop, so I have no way of contacting her. The specimen I had in mind when I first posted these topic was labeled from Hot Springs, Ark. No mention of irradiation. There have actually been a few natural smokeys from there. There was some additional information on the index card, however, that makes me think that it was irradiated. The specimen was from a 17 piece lot, which weighed 18 lbs. It was purchased from Kenmar Minerals in El Paso in 1964. Too abundant to be real!

Most of the radiation induced smoky quartz in the USA, and in fact I think the world is low grade specimens from Arkansas that have been turned nearly black by gamma radiation. Some dealers have shipped of thousands of pounds to food processing companies where they run stuff through gamma radiation by the pallet full. They usually just give it a real good dose and don't bother trying to give it just enough to make it a natural looking smoky color, they just turn it all black. If your specimen is one of these almost black looking specimens, the chances are very good it has been treated artificially.

Rock Currier
Crystals not pistols.

While perusing the website this hot July 4 day, I came across this old smoky quartz discussion. In one small Monroe County location I have found about 30 examples of dark smoky quartz Indiana geodes, one of which I have pictured here on the right. Others are pictured in the "midwest sedimentary geode" thread. Every geode collector seeing these marvels at them and is dumbfounded as to their specific color origin. These geodes have been found both broken and intact. Many have very dark and very lustrous quartz tips as seen here. They are scarce, mixed with numerous ordinary quartz geodes. So are ALL smoky quartz examples from ALL OVER irradiated or could there be some other reason giving the crystals their dark smoky color. I suggest, from my Indiana examples, in a non radiation sedimentary environment (other than a nuclear powered alien spaceship buried about 100 feet below the area where these examples come from) such possibilities as micro petroleum inclusions in the crystals or just an odd play of light thru otherwise colorless quartz. Just how did my examples get to be their very dark smoky color? Any thoughts?

micro petroleum inclusions in the crystals !!! Bitumin coloured quartz xls have precipitated oil drilling in St Lawrence Lowland Limestones.

Putting a SW light on them should prove if it is petroleum.

I kind of like the nuclear powered alien space ship explanation. Bet you could sell the specimen for more with that story.

Rock Currier
Crystals not pistols.

This is a broad subject.

Food irradiation applied to hamburger "patties" could have saved a number lives un-necessarilly sacrificied to Ecoli infection.

But because "radiation" is considered unsafe, it is not standard procedure. Dumb.

Is it "smoky" or "smokie" ?

My observations about natural versus un-natural smoky quartz are that the bases of un-natural smokys are often white.

My experience also, is that every smoky quartz I've ever collected from a pocket, and I've collected thousands of them, is that they are smoky evenly from base to termination.

I have collected loose smoky quartz crystals which were half in the soil and half exposed. The exposed halves are colorless, I presume from UV radiation.

I know of two universities which have cyclotrons that have been utilizied to convert white and colorless quartz to smoky quartz. In both cases the quartz was processed in bulk. I think cyclotrons require vacuum so these operations were probably clandestine and not approved by the university.

The University of Washington, where I believe some synthetic smokys (smokies) were produced once had a lovely cyclotron with an outdoor viewing area of the interior. Completely fascinating. It became improper according to the regents. I think it's now a greenhouse or some such other nonsense.

Bart

Since most smoky quartz owes its color to formation of color centers via radiation, it's going to usually be difficult to tell whether the radiation occurred in nature or in a reactor or accelerator. If there were few defects in the quartz to begin with, and they were introduced via irradiation with neutrons, there may be some residual radioactivity. If the particles used were low-energy x-rays or electrons, you might see a gradation in the coloring in the specimen. However, this can happen in nature. I think this would be tough to detect.

Most bulk irradiated quartz are as Bart described and easily recognized. Thankfully it is not worth the effort to do a really good job which as Ray suggests would be undetectable.

This subject and related threads go back several years and there has been much discussion. Several days ago I asked a specific question whether ALL smoky quartz from ALL locations was "smoky" secondary to irradiation or could there be other origins for the smoky quartz color. I gave my Indiana geode example as possibly a specimen with another plausible origin for its smoky color. The blogs immediately after my question seemed to adequately answer my specific question. And using UV light seems to confirm micro petroleum inclusions as a second plausible explanation for the smoky quartz color. Now, these most recent blogs have gotten off my specific question and reverted back to the extensive previous discussions of smoky quartz. These blogs are now just reiterating similar earlier blogs. CHEERS.........BOB



Edited 1 time(s). Last edit at 07/06/2012 06:45PM by BOB HARMAN.

Bob, I have some dark "smoky" quartz in trap rock vesicles (from East Haven, CT) associated with goethite, hematite and calcite (for example [www.mindat.org] ). These appear to get their smoky color from included hematite. Some crystals (not many) show a smoky phantom inside the quartz, possibly from depletion of the hematite before the quartz completed formation.

"Phantoms or color zones are not helpful either. The color in smoky quartz develops long after the crystal growth stopped."

What about Brandberg Quartz where you get alternating zones of smokey and amethyst that appear to correspond to internal phantoms? That seems to be coloration during the crystal growth?

"That seems to be coloration during the crystal growth? " - not really. The amethyst seems to be due to Fe+3 while smoky is due to Al (these are in the ppm concentrations). Irradiation then generates the colors.