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Maxilos
Joined: 02 Nov 2010
Posts: 191
Location: Boskoop, The Netherlands
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Posted: Nov 15, 2011 13:39 Post subject: Re: Minerals and fluorescence |
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Wow, this is weird. That was just something I came up with and it could actually be correct! Thanks for supporting my theory!
Other theories are welcome too!
Mark
_________________ "Still looking for the philosopher's stone" => Dutch proverb |
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Roger Warin
Joined: 23 Jan 2013
Posts: 1177
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Posted: May 20, 2013 06:26 Post subject: Luminescence - Fluorescence |
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Hello,
Fluorescence can be initiated by photons of different energy (frequency). There are not only long and short UV rays that induce luminescence. Here spinel excited by a green laser (532 nm).
Spinel from Mogok, Myanmar.
Roger.
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Spinel Mogok, Myanmar 8 mm Fluorescence with a green laser |
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Riccardo Modanesi
Joined: 07 Nov 2011
Posts: 618
Location: Milano
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Posted: May 20, 2013 07:53 Post subject: Re: Luminescence - fluorescence |
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Hi Roger!
Interesting! How can I get this kind of light? Is it commonly available or is it just a laboratory device? If the former possibility is right, it would be interesting as an analysis instrument for faceted or cut stones as well!
Greetings from Italy by Riccardo.
_________________ Hi! I'm a collector of minerals since 1973 and a gemmologist. On Summer I always visit mines and quarries all over Europe looking for minerals! Ok, there is time to tell you much much more! Greetings from Italy by Riccardo. |
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Jordi Fabre
Overall coordinator of the Forum
Joined: 07 Aug 2006
Posts: 4900
Location: Barcelona
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Posted: May 20, 2013 10:11 Post subject: Re: Luminescence - Fluorescence |
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Roger Warin wrote: | Hello,
Fluorescence can be initiated by photons of different energy (frequency). There are not only long and short UV rays that induce luminescence. Here spinel excited by a green laser (532 nm).
Spinel from Mogok, Myanmar.
Roger. |
Posts merged to this other thread: Minerals and fluorescence for better visibility and coherence.
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Roger Warin
Joined: 23 Jan 2013
Posts: 1177
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Posted: May 20, 2013 10:54 Post subject: Re: Minerals and fluorescence |
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Hello Ricardo,
This is not problem. The laser comes from China (10 or € 15).
The only problem is to fix the device switched pointing spinel.
Proficiat.
Roger.
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chris
Site Admin
Joined: 12 Jul 2007
Posts: 538
Location: Grenoble
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Posted: May 20, 2013 11:28 Post subject: Re: Minerals and fluorescence |
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Hi Roger,
Maybe I'm a bit paranoid on that, but is it a good idea to illuminate mineral specimens with laser beam ? of course the light produced by such device is far less energetic than the energy of lab or military lasers, but I'm wondering if exposing colored minerals to laser beam could damage them knowing the light remains much stronger than daylight light ?
As discussed in this thread: How to minimize Arsenic on Realgar, I don't think it would be wise to use such green light laser on realgar...
Any idea on that ?
Chris
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Roger Warin
Joined: 23 Jan 2013
Posts: 1177
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Posted: May 20, 2013 15:51 Post subject: Re: Minerals and fluorescence |
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Hello,
This is a very interesting question.
From a fundamental point of view, the physical chemist is not interested in the stability of the molecule when it is analyzed. Everything depends on the technique used.
However, the luminescence is a gentle technique. It does not destroy the sample in any way. The luminescence emission gives a cold light, unlike incandescent one, which gives an emission spectrum, which corresponds to a warm light.
Photons used with a green laser cause a small excitation of some electrons in the atom or molecule, which fall to the original level by emitting energy. In the case of luminescence (or fluorescence), this form of light energy appears but with a change in wavelength. The invisible UV excitation light becomes visible (blue, red, yellow ...).
The case of realgar (As4S4) is very different. The light energy from the sun is sufficient to initiate a chemical decomposition (redox). We finally obtain orpiment (As2S3), but accompanied by As2O3 with the presence of air. But the situation is very complex, because it also gets in the early stages, some polymorphs of realgar as pararealgar (different molecule from orpiment). This aspect of inorganic chemistry is very complex.
In fact, realgar is a rather unstable crystal structure and a small supply of energy like light, can destroy it.
It is very far from the situation of a simple, highly resistant molecule as spinel (this mineral is refractory to high pressures and temperatures) slightly tickled by relatively small energetic photons (X-ray fluorescence is also possible).
The fluorescence excitation is a phenomenon which lasts from 10-9 to 10-6 seconds.
Roger.
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Mark Ost
Joined: 18 Mar 2013
Posts: 516
Location: Virginia Beach
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Posted: May 20, 2013 19:04 Post subject: Re: Minerals and fluorescence |
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Hi Roger. I have wanted to do this with my Mogok spinel and will get around to it this week end. Also wanted to try with a couple of ruby conundrums I have. Odd though. If you get the electron too energized it may jump a couple of levels and dissipate the energy of it falling in the form of heat or lattice vibration vice photon emission. I love the picture.
Ricardo, any astronomy supplier has these. I am a bit leery of some of the really powerful ones that some folks have made. Far too powerful for responsible use.
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Roger Warin
Joined: 23 Jan 2013
Posts: 1177
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Posted: May 20, 2013 22:51 Post subject: Re: Minerals and fluorescence |
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Hello Mark,
I cannot explain here the details of the fluorescence. The excited molecule returns to its stable level by several processes (heat dissipation, vibration and rotation ...). But it happens that the radiative energy is dissipated. First, small electron energy dissipation occur before the last jump (fall) to give the fluorescent photon. It is due to what is called as the Stokes shift.
In general, there is no fluorescence because the dissipation is so trivial by the general process and because there are no activators.
Some atoms promote fluorescence, such as REE or manganese. The site manager must possess many vacant orbitals poorly differentiated. Cerium is a frequent activator (fluorophore center). And as it is abundant on Earth and its steric hindrance is similar to that of calcium, it often replaces it in the crystal lattice.
If there are activators of fluorescence, there are also poisons of this phenomenon. They are inhibitors of fluorescence. They are common and they affect the immediate environment of the fluorophore center. Fluorescence is a random phenomenon in practice in geology.
The fluorescence is a technique widely used in biophysics in the study of proteins.
Roger.
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Mark Ost
Joined: 18 Mar 2013
Posts: 516
Location: Virginia Beach
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Posted: May 21, 2013 03:15 Post subject: Re: Minerals and fluorescence |
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You are right on about random process. I don't recall any time spent on fluorescence in school. I suspect, like color, it is so highly variable in minerals it was shelved in favor of more certain techniques for mineral identification. It is a fascinating quality though and I have an entire case dedicated to it.
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Josele
Joined: 10 Apr 2012
Posts: 407
Location: Tarifa, Spain
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Posted: May 21, 2013 08:29 Post subject: Re: Minerals and fluorescence |
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For someone really interested in mineral fluorescence, is highly recommended to read the books related below:
- Luminiscence in mineral kingdom
- Luminiscence specroscopy of minerals and materials
The first one explains luminiscence in a easy way and contains many very nice pictures of fluorescence.
Second one is more technical and focused in activators determination, with spectrographics of many minerals with diverse activators.
Reading these books marks a before and after in the knowledge and understanding of the luminescence phenomenon.
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- Luminiscence in mineral kingdom, Guido Mazzoleni, edited by Sandit in 2012 |
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Luminiscence specroscopy of minerals and materials, Michael Gaft et al., edited by Springer in 2005. |
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Afghanite on calcite Badakhshan, Afghanistan 6 x 3 x 2,5 cm
1- halogen lamp 2- LW UV 3- SW UV |
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_________________ Josele |
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