Help mindat.org|Log In|Register|
Home PageMindat NewsThe Mindat ManualHistory of MindatCopyright StatusManagement TeamContact UsAdvertise on Mindat
Donate to MindatSponsor a PageSponsored PagesTop Available PagesMindat AdvertisersAdvertise on MindatThe Mindat Store
Minerals by PropertiesMinerals by ChemistryRandom MineralSearch by minIDLocalities Near MeSearch GlossaryMore Search Options
Search For:
Mineral Name:
Locality Name:
Keyword(s):
 
The Mindat ManualAdd a New PhotoRate PhotosLocality Edit ReportCoordinate Completion ReportAdd Glossary Item
StatisticsThe ElementsMember ListBooks & MagazinesMineral Shows & EventsThe Mindat DirectoryHow to Link to MindatDevice Settings
Photo SearchPhoto GalleriesNew Photos TodayNew Photos YesterdayMembers' Photo GalleriesPast Photo of the Day Gallery
bannerbannerbannerbannerbannerbanner

Irradiated and natural smoky quartz

Posted by Howard Heitner  
avatar
Howard Heitner February 13, 2009 05:55PM
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?
avatar
Ronald John Gyllenhammer February 13, 2009 11:18PM
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.

http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-14392005000300014
avatar
Ronald John Gyllenhammer February 13, 2009 11:39PM
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
avatar
Claus Hedegaard February 15, 2009 09:46PM
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.
avatar
Ronald John Gyllenhammer February 16, 2009 01:46PM
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
avatar
Amir C. Akhavan February 16, 2009 03:30PM
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
avatar
Alfredo Petrov April 05, 2009 03:12PM
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.)
avatar
Howard Heitner April 05, 2009 07:37PM
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!
avatar
Rock Currier April 06, 2009 04:19AM
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.
avatar
Bob Harman July 04, 2012 07:33PM
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?
open | download - DSC02179.JPG (974.7 KB)
avatar
Rob Woodside July 04, 2012 08:56PM
micro petroleum inclusions in the crystals !!! Bitumin coloured quartz xls have precipitated oil drilling in St Lawrence Lowland Limestones.
avatar
David Von Bargen July 04, 2012 10:39PM
Putting a SW light on them should prove if it is petroleum.
avatar
Rock Currier July 05, 2012 03:50AM
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.
avatar
Bart Cannon July 05, 2012 12:04PM
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
avatar
Ray Ladbury July 06, 2012 03:38PM
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.
avatar
Rob Woodside July 06, 2012 06:29PM
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.
avatar
Bob Harman July 06, 2012 06:41PM
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.
avatar
Fred E. Davis July 06, 2012 07:18PM
Bob, I have some dark "smoky" quartz in trap rock vesicles (from East Haven, CT) associated with goethite, hematite and calcite (for example http://www.mindat.org/photo-339255.html ). 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.
avatar
Mike Keim July 07, 2012 04:27AM
"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?
avatar
David Von Bargen July 07, 2012 03:25PM
"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.
avatar
Jeff "Mouse" Jessie September 27, 2014 12:42AM
Hey guys, I work at a Rock Shop and have just gotten in some Smoky Qtz. originating in Brazil. Some are very dark some are rather pale, I have variegation, Veils, color zoning, etc.. I have read through the posts here and have a question that perhaps one of you may be able to answer. This lot of Brazilian Smoky Qtz. xtls, many of the xtls have pyrite crystals just beneath the surface and on the surface, what I know of Irradiation on Sulfide minerals is that it results in oxygen and water replacement in the sulfide mineral and forces oxidation and thus removes the sulfide, this is a practice used in coal production to lower the sulfides in the coal before burning. I have read a number of studies all of which suggest that Pyrite Crystals would not survive Irradiation from most available methods. As I said before these xtls are A-B quality Brazilian with solid color on most from base to termination, many with Pyrite xtls on the surface that are intact and very sparkly, a number of the xtls are nearly perfect in clarity and lack inclusions that you would likely see in heated quartz, so I doubt that they have been heated as in the process that is used to lighten quartz before irradiation to darken it. I have seen a lot of irradiated qtz. in my time and usually can recognize it on sight but this batch has got me wondering cause though much of it is dark, it is not outside the color i have seen on natural specimens, some of these xtls even have that slightly golden molasses color that some of the really nice natural Smokey's have. So anyway what do you think of the possibility that these are natural based on the presence of intact Pyrite Crystals?

Earth Junkie
avatar
Doug Daniels September 27, 2014 01:16AM
I think the "experts" here would want to see some photos of some of them; it's always helpful. We may not be able to tell you much from just a description (then again....I'm not one of the "experts").
avatar
Amir C. Akhavan September 27, 2014 11:55AM
No need for photos.
If what you say is correct, why are there still pyrite crystals included?
Smoky quartz is always irradiated.

... irradiation to remove S from coal must be the reason why I pay $500 per KWH ...
avatar
Owen Melfyn Lewis September 27, 2014 05:35PM
Jeff,

There are two pre-requisites to create smoky quartz, whether in nature or in the lab
1. A very small percentage of the Si+++ atoms are replaced by Al++++ atoms (c. 0.0001%). This is true of most quartz found in nature. Charge neutrality is maintained by H+ protons trapped interstitially in the lattice.
2. Such material is irradiated, the energy detaching an electron from an O-- atom adjacent to an Al atom. This free electron is attracted by an H+ proton to create a neutral H atom. The electron deficient O- will then absorb incident light.

The above is equally true whether the process is naturally or artificially caused.

Since it is known that pyrite crystals do sometimes exist in smoky quartz, it follows that pyrite is not destroyed at the low level of irradiation required to turn quartz smoky.

Though almost all natural quartz contains trace amounts of Al, only where there is (or once was) a natural source of irradiation does smoky quartz form naturally. Heating can reverse this process and subsequent re-irradiation re-instate the smokiness.

For more (lots) on electron and hole centres and colour centres, take a squizz at Chapter 9 of 'The Physics and Chemistry of Color' by Kurt Nassau.



Edited 2 time(s). Last edit at 09/28/2014 05:52PM by Owen Melfyn Lewis.
avatar
David Heller July 10, 2015 02:21AM
Pardon my piggy-backing onto this thread, but this is the first time I have seen information on pyrite inclusions in quartz. First, why is it so uncommon to find inclusions of pyrite in quartz crystals? I am attempting to find a camera that will capture the three mineral inclusions found in some quartz crystals from a mine location in western Nevada county California. Decades ago I used to ravage the tailing piles of the Liberty gold mine with four tunnels near Lake Spalding. Most of the crystals from the lower tunnels have a pitted surface appearance from chlorite that had disappeared, but often there was a clear "cap" of quartz that shows the underlying chlorite phantom with pyrite micro-cubes in a layer above the chlorite. Nearer the base of the xtal, and dimly seen through the rough and dirty side surfaces are mostly three sides phantoms of a white mineral who primary shape looks like double pointed dogtooth calcite. In the tailings of the tunnels higher up the quartz vein, the crystals were prettier, more like regular crystals with nice micro pyrites and complete chlorite phantoms. The topmost diggings produced some of the brightest quartz I have seen outside of Arkansas or now, Nepal. These crystals had no chlorite just pyrite or the white phantoms with pyrite phantoms nearer the surface. Sometimes the micro-pyrites formed a sheet just under the surface. Sadly this tunnel went in only six feet or more of these specimens would have been found. Illumination makes them sparkle. The challenge with polishing up some of the homelier specimens is that the pyrites are found right under the surface. I know that this unlearned description is probably making some of the experts roll their eyes, and it is rude to not have pictures accompany my text, but I hope to get some some with the help of a rockshop owners camera and will gladly post them on the site. Occasionally there is an odd shape for the pyrite/metal inclusions, more like a flat rectangular needle, but mostly the inclusions are the classic cube shape. The quartz from the lower portion of the tailings is the palest barely yellow hued smokey, but the upper tailing seems to be clear quartz.

ps. the tunnels are now blocked off and the site is an endangered bat species protected zone.
avatar
Rock Currier July 12, 2015 11:39PM
I don't think pyrite included in quartz is particularly uncommon. What is uncommon is to have well formed large pyrite crystals (say of about a cm) included in clear quartz.

Rock Currier
Crystals not pistols.
avatar
David Heller July 13, 2015 02:27AM
Thanks for correcting me sir, I trust that your experience and knowledge are greater than mine.
Spam prevention:
Please, enter the code that you see below in the input field. This is for blocking bots that try to post this form automatically. If the code is hard to read, then just try to guess it right. If you enter the wrong code, a new image is created and you get another chance to enter it right.
CAPTCHA
Your message:
Attachments:
  • Valid attachments: jpg, jpeg, gif, png, pdf
  • No file can be larger than 9.38 MB
  • 3 more file(s) can be attached to this message



bannerbannerbannerbannerbannerbanner
Mineral and/or Locality  
Mindat.org is an outreach project of the Hudson Institute of Mineralogy, a 501(c)(3) not-for-profit organization.
Copyright © mindat.org and the Hudson Institute of Mineralogy 1993-2016, except where stated. Mindat.org relies on the contributions of thousands of members and supporters.
Privacy Policy - Terms & Conditions - Contact Us Current server date and time: December 10, 2016 12:45:52
Go to top of page