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EducationNew glossary entry for "radiation burn"

7th Dec 2019 17:28 UTCEd Clopton Expert

I have added a glossary entry for "radiation burn" and would welcome constructive feedback.  I attempted to include photo #101736 as a head photo by putting its number in the box at the bottom of the edit screen but it doesn't yet appear.  Is there something else I need to do to add this (or a different) photo?

7th Dec 2019 18:55 UTCJolyon Ralph Founder

I don't believe 'radiation burn' is the correct term here - nothing has burned. 

I did a quick search on 'google scholar' for radiation burn quartz and have not found any use of it in the way you describe.

Now, as to what the name should be I don't really know. Perhaps there isn't anything better, but I'd like to see what others have to suggest.

7th Dec 2019 20:01 UTCRalph Bottrill Manager

I have only heard this term used for burns received by people and other organisms from intense, high energy radiation, but not in minerals.

We already have the glossary term pleochroic halo which describes the coloured halos or aureoles formed in many micas, chlorites and other minerals, around radioactive inclusions. The term may not be really appropriate as pleochroism refers to colour changes in different orientations, which does not really  seem to apply to this effect. A better term is radiohalo, used as a synonym of the above term. A more descriptive term is RICHs: radiation-induced colour halos, but I need to add it.

7th Dec 2019 20:59 UTCFrank K. Mazdab Manager

Pleochroic halos or "radiohalos" (or "RICHs") really are pleochroic, however, at least in an anisotropic host, as is demonstrated in this video of monazite inclusions in cordierite from Moose River, New York:




8th Dec 2019 08:22 UTCRalph Bottrill Manager

OK thanks Frank I cannot argue with that one! But Im not sure its usually that obvious, or I haven't studied them hard enough?

8th Dec 2019 10:00 UTCFrank K. Mazdab Manager

Although the set of halos in this video are particularly exemplary, pleochroism in halos is pretty typical, and likely a function of the anisotropy of the host.

I suspect, although I've never had an opportunity to test this, that halos in an isotropic host material would be non-pleochroic, unless the radiation damage itself caused some local anisotropy. But I also can't think offhand of an isotropic mineral where I've ever seen halos, even in other ferro-magnesian silicates like garnet that might seem like prime candidates?  I suppose for an alternative test, a sample containing a halo-susceptible mineral such as the cordierite in my video could be sectioned so one of the optic axes of the cordierite was perpendicular to the stage, and then searched for halos.  If seen, I would guess these halos would be at best minimally pleochroic, or perhaps even entirely non-pleochroic?  Or maybe not?

But maybe also, they might not even be seen at all?  Apparent from the video is that there is a particular grain orientation where the halos practically disappear; if that orientation just happens to be Y parallel to the lower polarizer (I've never tested this, so I don't know), then one would never see any halos in a cordierite oriented to give a centered optic axis figure (where all rotations would show Y), even if those halos would be abundantly obvious in a different orientation.  I'm sure someone must have tried this before... probably back in the 1800s.

I also wonder that the actual pleochroism effect may be less noticeable in a sheet silicate like biotite (compared to cordierite), because I suspect the halos are most readily observed when the cleavages are in the plane of the thin section (in fact, I can't recall seeing halos in biotite grains oriented differently, even in the same samples where other grains do show halos.)  In any case, when the cleavage is parallel to the plane of the thin section, this orientation is almost looking straight down the optic axis of a low 2V° mineral like biotite. As speculated above with the cordierite, in a near-isotropic orientation, perhaps pleochroic halos just aren't pleochroic??

In these quartz "radiation burn" centers of "smokiness", I wonder if in a thick enough section, if any of the darkest colored areas would be sufficiently color saturated to actually show a discernible difference from the adjacent colorless quartz, and then furthermore, if any such recognizable color would show pleochroism in appropriately-oriented sections?

8th Dec 2019 20:19 UTCRalph Bottrill Manager

Very interesting thoughts Frank, I may need to recheck this effect. As you say we usually see the halos best in biotites and chlorites looking down the optic axis more or less, in cross section they tend to be messy to visualise. It would also be interesting to see if thick sections of quartz etc show the pleochroism ( too faint in think sections).

7th Dec 2019 21:20 UTCKevin Conroy Manager

Ed, could the photo be posted here so we can have a look?

7th Dec 2019 23:29 UTCEd Clopton Expert

09606330015757371104143.jpg
Oops, well, it's a term I've heard off and on over the years, and it's used and understood by collectors here in New England (at least here in Maine) to describe dark, smoky spots on white quartz where it has been in contact with radioactive minerals, so I thought it was more universal.  If it's an obscure or regional usage, that may be all the more reason to have it in the glossary.  I'm happy to edit the entry, putting "burn" in quotes and explaining that it's an informal, figurative vs. literal, non-scientific term.  I considered that at first but decided against it in the interest of conciseness (never my long suit!).

As to whether it's a burn or not, medicine defines trauma as injury caused when tissues absorb energy from outside themselves.  (I'm a paramedic and ER technician by training.)  The vast majority of trauma is due to kinetic energy, but to bring burns inside the trauma tent where they belong, "energy" is broadened to include thermal, chemical, radiation, and electrical energy.  By that definition (whether it's relevant here or not I'll leave to the professionals) these spots would constitute burns.

The photo I hoped to include is shown above (specimen 9 cm wide, Consolidated quarry, Georgetown, Maine).  Similar material occurs in a number of U-bearing pegmatites in southern Maine.  I have also seen specimens from Brazil, and I'm sure they occur elsewhere as well.  I see now that I had left a digit out of the photo ID--should be 1017306--so that might explain why I couldn't get it to appear.

8th Dec 2019 00:58 UTCAlfredo Petrov Manager

I have heard the term "radiation burn" used before for the darkening of quartz and felspar around radioactive minerals. Not the same thing as a "halo", because a halo is a ring-shaped structure, as seen in Frank‘s photo, which I‘ve seen too in micas around very tiny radioactive inclusions, although I suppose the halos are subsets of radiation burns. (A halo cannot form around a larger grain - It requires almost a point source of radiation.)

Googling the terms radiation burn and halo, I find them used in compound form in print by our very own Phil Persson:

Mineralogically, microlite forms small crude to somewhat euhedral octahedral crystals to 1 cm. with a resinous brown to black luster and distinctive radiation ‘burn halo’s’ in the surrounding lepidolite. These crystals are often quite radioactive and may in fact be uranomicrolite.

Am not commenting on whether the term is a good one to promulgate or not, but just defending Ed Clopton by showing he did not make the term up in his dreams, and it probably should be in the Glossary, even if the entry just points towards another more approved term elsewhere.

8th Dec 2019 01:28 UTCClifford Trebilcock

Do a quick search on Mindat under "Quartz with radiation burns" more examples are posted.

Cliff

8th Dec 2019 02:02 UTCKevin Conroy Manager

Ed, thank you for adding the photo.   The following is an interesting short article that has another variation of the "halo" name:  

8th Dec 2019 03:31 UTCEd Clopton Expert

Thanks, everybody, for your input.  Searching as Cliff Trebilcock suggests (using Search located right below Login/Logout:  Search For = Photos, Mineral Name = Quartz, and Keyword(s) = "radiation burn") produced 11 photos with features described as radiation burns.  Except for three dealer-uploaded specimens from Pakistan, all specimens were from Maine localities and all but one of the remaining uploaders I recognized as being from Maine or nearby.  That supports the idea that it's a regional term.

I'll work on revising the entry tomorrow.

8th Dec 2019 08:27 UTCRalph Bottrill Manager

Well OK it certainly sounds like its in common enough usage to have listed here. Maybe radiation haloes are a subset of radiohalos, in turn a subset of radiation burns?

8th Dec 2019 09:00 UTCJolyon Ralph Founder

I have no doubt that the term is used within the collector community, but is it something that we should be promoting as a scientific term within our glossary?  There are a lot of terms that are used confusingly/incorrectly within the collector community, surely we should be trying to clarify these at least with a disclaimer that this is not a professional term?

8th Dec 2019 16:40 UTCEd Clopton Expert

A function of the Mindat glossary should be to help differentiate between rigorously defined scientific terms and informal terms used by collectors and dealers.  I can easily imagine someone turning to Mindat to find out what the heck a "radiation burn" is, and we should be able to oblige him/her, as well as pointing out that, by the way, it's an informal term that a real mineralogist is not likely to use in describing the phenomenon.

How about this:

Radiation burn: an informal, non-scientific term for a dark spot (commonly on quartz) caused by gamma* radiation from a minute particle of a radioactive mineral. Over time the radiation disrupts the host mineral's crystal structure in the vicinity of the radioactive particle, affecting the way light passes through it and making it appear dark. In quartz, the process effectively creates a local zone of smoky quartz in otherwise colorless quartz. Because the discoloration remains if the radioactive mineral is removed by weathering or cleaning, a specimen with radiation burns is not necessarily radioactive, although its level of activity should be checked with a Geiger counter.

See also:  pleochroic halo; radiation induced color halo (RICH); radiohalo

*Should we specify gamma radiation?  The entry for pleochroic halo attributes the damage to alpha decay, and the article referenced under radiation-induced color halo attributes it to beta and gamma radiation.  Just leave out the Greek letter and call it "radiation"?

Once we have this settled--speaking of informal, non-scientific terms--who wants to take on "elestial"?

8th Dec 2019 17:12 UTCJolyon Ralph Founder

I'd say leave it as 'radiation'.

8th Dec 2019 17:41 UTCChester S. Lemanski, Jr. Manager

The term that I have used most often is a "radiation halo." 

8th Dec 2019 18:15 UTCRobert Nowakowski

In the Bancroft Ontario area we have used both radiation burn and reaction rim to refer to this.

8th Dec 2019 20:38 UTCRalph Bottrill Manager

Ed that sounds very good thanks. I would imagine the alpha radiation does most of the real damage, as with people, but best to make it “ionising radiation” rather than just radiation as most of the latter is harmless. I doubt if most such specimens contain enough radioactive material to be a concern as you are generally looking at sparse microscopic grains and you really need at least a gram or so of Uranium to cause significant health issues in display specimens.

9th Dec 2019 00:01 UTCEd Clopton Expert

I have updated the entry largely as proposed above.  Anyone with glossary-tinkering privileges is able to revise it further if needed.  The photo still does not appear; do I need to do more that just enter its Mindat photo # in the Head Photo box on the Edit screen?  If someone has better photos, they would be welcome in place of or in addition to the suggested one.

11th Dec 2019 12:10 UTCEd Clopton Expert

After several Edit attempts the photo still hadn't appeared, so I tried adding a photo of a second specimen.  Now both photos appear with the glossary entry.

11th Dec 2019 14:18 UTCMark Andrews

I'd like to suggest an alternative photo for the "radiation burn" glossary entry:
Photo ID: 943214

The reason I am suggesting this photo is because you can actually see the radioactive brannerite needle that is causing the "radiation burn" unlike the two photos currently displayed in the glossary entry.

11th Dec 2019 21:17 UTCEd Clopton Expert

Good addition.  Thanks.  I have a specimen or two with halos around scales of autunite, but this is a more dramatic example.

11th Dec 2019 20:23 UTCRalph Bottrill Manager

Added, thanks Mark and Ed.

12th Dec 2019 02:08 UTCFrank K. Mazdab Manager

The preceding brannerite example in particular seems like it could be equally defined as a pleochroic halo (a really big one!) than as a "burn". But to each their own definition.

Also, just for fun, I did remember I in fact do have an example of non-pleochroic "pleochroic halos" in an isotropic substance... here's a video of halos around presumed rosenbuschite prisms in fluorite, from Norra Kärr.  Although there's purple immediately next to the tan inclusions, a bit further out around each grain is an "anti-halo" where the fluorite is colorless, followed still further out by a dark purple rim. And none of the fluorite coloration changes with rotation, as expected from symmetry constraints.




12th Dec 2019 19:20 UTCUwe Kolitsch Manager

I get an error message (using latest FF):
Video unavailable


12th Dec 2019 19:47 UTCFrank K. Mazdab Manager

oops... my mistake... I had it set to not-embeddable, but I've fixed that. Should be viewable here now.

12th Dec 2019 19:51 UTCRalph Bottrill Manager

Works on Safari. Interesting thanks Frank, and adds to the question of what the coloration in fluorite means.

12th Dec 2019 20:46 UTCPaul Brandes Manager

Able to see here on FF with no problem.
Uwe, did you get it to work?

13th Dec 2019 15:02 UTCUwe Kolitsch Manager

Yep, it works now.

12th Dec 2019 21:35 UTCEd Clopton Expert

The fact that some "pleochroic halos" are not pleochroic raises the obvious question of why they are called that in the first place.  Seems like the more general "radiation halo" would be a better term, with the corollary that the halos can be pleochroic* in non-isotropic minerals.  (*or necessarily are pleochroic? I don't know much about optical mineralogy.)

13th Dec 2019 01:13 UTCFrank K. Mazdab Manager

well, as has been conveniently pointed out on another thread, there are only ~435 isometric minerals (which would make up the overwhelming majority of isotropic minerals), out of some ~5323 total minerals. And common isotropic minerals like garnet and spinel that frequently host radioactive mineral inclusions seem to be "immune" to radiation-induced halos. Isometric fluorite appears susceptible... perhaps isometric halite might be also be susceptible, if halite could enclose radioactive minerals, but its paragenesis just isn't ideal for that.  So we have one definitive "non-pleochroic" example (although presumably out of 435 possibilities, there must be a few others too?)

But all other crystal systems are permissive to pleochroism. So "pleochroism" in halos would seem to be the rule rather than the exception. It's also possible they were named "pleochroic" halos well before radiation was even a known or well-understood phenomenon?

15th Dec 2019 13:39 UTCNick Gilly

Frank, isn't the colour of deep blue halite caused by natural irradiation?

15th Dec 2019 20:02 UTCFrank K. Mazdab Manager

Hi Nick,

Yes, I believe that is the prevailing theory for blue/purple in halite, but above I was referring more specifically to halos around radioactive inclusions, which I wouldn't have typically expected to be present given how halite forms.

But, in wanting to add some color to my answer (heh heh), I ran across an interesting paper where the authors not only did observe haloed and "anti-haloed" inclusions in halite (so the latter a bit like my bleached anti-halos in Norra Kärr fluorite) in some Polish halite, typically of a potassium-bearing (hence K-40 bearing) mineral like sylvite or carnallite, but also observed local optical anisotropy in the halite. While the anisotropy was presumably related to stress, it still made me wonder (and the authors didn't indicate) whether the blue/purple areas that were of lower symmetry were also pleochroic... (salty) food for thought.

 
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