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405 nm laser pointer and calcite

Posted by Henry Barwood  
Henrik Friis October 21, 2010 03:34PM
Hi Donald,
Yes that is why many minerals will show the same luminescence, especially when you start exciting in the visible region. A lot of minerals have very broad excitation bands in the UV region, and as these can have a "tail" into the visible region your 405 nm laser might also these in addition to Sm3+. This might be the case of the calcite you mention.

And weather this has any usage or not, I believe it does. I think a lot can be learned, and new ideas created for the material science community, by looking at natural minerals. At the moment a lot of research focus on generating low energy consuming lighting in the form of LEDs, dosimetry badges or security marking all utilizing luminescence.
Donald Vaughn October 21, 2010 04:48PM
I was thinking more from the mineralogy point of view. Obviously from the material science, and physics point of view many potential uses are obvious from new types of lasers to new types of "quantum dots". I'm assuming the levels of Samarium in these minerals is extremely low and I suppose its possible that this luminescence could be used for product tagging. I was even considering getting a nice clear Durango Apatite and trying to cut and polish a laser crystal from it, the A.R. coating was going to be the tough part.
I was still in the mineralogy mindset when I posted the comment about the usefulness.
Henrik Friis October 21, 2010 06:05PM
Natural minerals have so many impurities influencing the luminescence, i.e. both foreign or displaced elements and vacancies, that I think it would be difficult to use them directly in a commercial way. And just because a fluorapatite from one locality works well, there are no guarantee that fluorapatite from the neighbouring locality will. Having said that, I have found that I am able to turn on different emission centres independently of each other, or all simultaneously in some natural minerals, in theory making it possible to create low costs multi frequency materials.
Donald Vaughn October 23, 2010 05:27PM
more of an experiment really I know that the distribution of Samarium is probably quite variable even in a single crystal as well as lattice distortions it probably would not work . there a Samarium doped Calcium fluoride lasers already so we know at least in some instances Samarium is used as a dopant though in a more controlled and refined manner
Berthold Weber November 09, 2010 07:30AM
Here is a sample of colourless-white Opal-AN (Hyalite) which you can see fluorescing green in 405 nm Laserpointer UV light. Tubussis 22 farm, Karibib District, Erongo Region, Namibia. FOV = 6 mm.

Edited 1 time(s). Last edit at 11/09/2010 07:33AM by Berthold Weber.
open | download - opal_erongo.jpg (310.7 KB)
JerryBear April 01, 2012 09:42PM
I have gotten very strong responses from a 5mw 405nm laser pointer. Orange calcites of the kind from New Jersey show intense orange pink fluorescence with very brief fiery orange phosphorescense. These are stones that glow orange red under SW and hardly react to LW. In stones cotaining calcite mixed with other minerals, i get large patches of deep orange fiery fluorescence that looks just like burning coals. Some SW minerals that do not respond to LW will sometimes show some of their SW color to far violet laser light. Could this be a frequency doubling effect from using laser light? I have some corundum with chromium pebbles that are undistinguished brownish lumps under visible light and just barely present a slight reddish color under LW but will glow with a really intense fiery purplish red under the laser beam. If you look at it through light amber lenses to screen out far violet the color will look exactly like strongly illuminated gem rubies. It is interesting that only these little pen lights will bring out the hidden kinship of basically industrial grade corundum with precious gem ruby! I have seen Terlingua type calcites glow a bright whitish color under the 405nm laser light rather than the usual pink to orange LW color. To get a less burning effect, try spreading the beam with a magnifying glass. The fully concentrated beam gives the best phosphorescence but the spread beam will show the same colors. I have several so called "ultraviolet flashlights" using lED's that operate in the Far Violet range from 380nm to 405nm but they produce very poor quality mineral fluorescent effects because they give off so much visible light. On the other hand I have a true LW UV 365nm LED flashlight and it works splendidly. The laser pointer is far purer, nearly all its radiation falling into the 405nm + _ 10nm range, I also suspect the intensity and coherence of the laser beam also favors fluorescent and phosphorescent effects. I think that FV or Far violet is an exciting new expansion of the field of study for those who love fluorescent minerals. It achieves brilliant eerie effects that you can see under no other kind of light and is significantly different from longWave ultraviolet light to be in a category of its own. You should get a 5mw laser pointer to be sure to have enough power to bring out all these effects. These are the strongest laser pointers that are generally recognized as safe. Only if you stare directly into the beam for more than a few seconds will it be likely to harm your vision. The only cases known of (fortunately temporary) eye damage from 5mw lasers concerned idiots who did exactly that! You can get a 5mw 405nm laser pointer for less than $10 on Amazon. They should be in the possession of every collector of fluorescent minerals. If you take it out in the field, please do not point it up into the sky or in windows or at other people. The beam can carry for many miles.
Cheers! JerryBear
Frank K. Mazdab April 06, 2012 09:39AM
Moroccan cerussite glows too with the 405 nm laser pointer, but since I'm color-blind I'll just guess it's a yellowish or greenish color... and quite bright!
Henry Barwood April 06, 2012 08:00PM
Good to know about the cerussite. I've been compiling a list of species responsive to the 405 nm wavelength for an upcoming article.

Henry Barwood
Troy University
Troy, Alabama USA
Frank K. Mazdab April 07, 2012 07:08AM
No problem, Henry. Three other species to add to your list are afghanite from Sar-e-Sang, some of the accompanying calcite (when you rapidly move the laser light over the calcite you get a very brief "ghosting"), and whewellite from Bilina, Czech Republic. The whewellite is phosphorescent and glows for about 10-15 seconds. The color of all three of these samples is a yellowish or greenish color I believe, but it would be wise to get a second opinion from someone with better color vision than I have. By the way, the cerussite is also slightly phosphorescent, for perhaps a second or two.
Timothy Greenland April 07, 2012 01:56PM
From a practical standpoint, I found mine very useful in identifying idrialite on the Culver Baer mine dumps last May. This despite California sunshine - that stuff really beams it out!

Pink calcite from the Tankerville or Snailbeach mines in Shropshire (England) show a strong orange reaction with good persistence. If you are quick, you can almost write your name on a big chunk! Weardale fluorite works a treat, and so do most cerussites, Bage mine phosgenite and matlockite give good yellow responses. Anglesites from Broken Hill (NSW, Australia) or from Parys Mountain (Wales, UK) react quite strongly - those from Sardinia seem variable - some do; some don't, and Autunite nearly takes off on a beam of emitted photons!

There are lots of things I haven't tried yet, but that is a start...


Henry Barwood April 08, 2012 12:25AM
Thanks Frank and Timothy. So far, I have a list of over 30 minerals that luminesce with the laser and will add these to it.

Henry Barwood
Troy University
Troy, Alabama USA
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