405 nm laser pointer and calcite

I bought a cheap laser pointer from China (405 nm - violet) and have found several things that fluorese in this near UV light (ruby is one). I was checking some calcites from Jones Mill, Arkansas and found that they luminesced and phosphoresced a medium pink in the beam. A quick survey showed that most of the calcites from the alkali syenites showed this same response. Expanding the investigation I tried a variety of other calcite with little luck. Finally, I tried some slices of fluorescent calcite-willemite from Franklin, NJ. The calcite was mostly dead to the violet beam, but to my surprise, there were patches that showed the same pink response as the syenite calcites.

Could this fluorescence be an activator like REE, and if so, why would small patches of it show up in the Franklin material? This has me puzzled, but until I can conduct some additional tests, I'm at a loss as to the origin of the fluorescence. Has anyone else observed this phenomenon?

Henry Barwood
Troy University
Troy, Alabama USA

Yes, a lot of my calcites react this way as well, from Calumet, some calc-silicate rocks, even from Book Cliffs. Terlingua calcite shows little if any effect however. The Calumet seems to show the brightest fluorescence of everything I have, but is more orange. I do have some Franlkin material that has one or two little spots that show a response as well.
A little off subject, but I found plaster on the walls and ceiling has a short phosphorescence in a dark room with the laser.

Hi Jim,

Fascinating. I'm very curious why there are isolated activated domains in the Franklin calcites. There is obviously something odd going on. I checked a few Indiana calcites and found very little response in them. I'm glad to know that the Terlingua calcites have low response levels. I was going to see if I had a piece I could check. The plaster could be from an organic additive. Most plastics and many organic chemicals I've checked have moderately strong responses at 405 nm.

Henry Barwood
Troy University
Troy, Alabama USA

Well, the Terlingua fluoresces white, not orange, although it has a couple of small patches which have faint orange.
It also looks like my XRF will finally happen!

Jim,

OK, didn't read your post about the Terlingua clacite well enough. I also discovered that some intensely SW fluorescent yellow fluorites from Bedford, Indiana also luminesce brilliantly with the 405 nm laser.I also located a box of Franklin slices and checked more calcite. The response varies from nil to fairly intense pink-orange.

Henry Barwood
Troy University
Troy, Alabama USA

It seems to me that a calcite should be selected to dissolve it in a weak and high purity acid (suggest freshly distilled acetic acid diluted tenfold before use) ) and see if one can isolate a residue. This after washing and drying can then be microprobed. Of course be sure there are no spurious inclusions in the calcite.

John Attard

San Diego.

I found this. Excerpt from Wikipedia:
Divalent manganese, in concentrations of up to several percent, is responsible for the red or orange fluorescence of calcite, the green fluorescence of willemite, the yellow fluorescence of esperite, and the orange fluorescence of wollastonite and clinohedrite.
So maybe most Franklin Mn was bound up in the other minerals, leaving none or little for the calcite.
Furthermore, certain impurities such as iron or copper need to be absent, to prevent quenching of possible fluorescence.
Or maybe the calcite has quenchers such as those?

Divalent manganese, in concentrations of up to several percent, is responsible for the red or orange fluorescence of calcite, the green fluorescence of willemite, the yellow fluorescence of esperite, and the orange fluorescence of wollastonite and clinohedrite. Hexavalent uranium, in the form of the uranyl cation, fluoresces at all concentrations in a yellow green, and is the cause of fluorescence of minerals such as autunite or andersonite, and, at low concentration, is the cause of the fluorescence of such materials as some samples of hyalite opal. Trivalent chromium at low concentration is the source of the red fluorescence of ruby corundum. Divalent europium is the source of the blue fluorescence, when seen in the mineral fluorite. Trivalent lanthanoids such as terbium and dysprosium are the principal activators of the creamy yellow fluorescence exhibited by the yttrofluorite variety of the mineral fluorite, and contribute to the orange fluorescence of zircon. Powellite (calcium molybdate) and scheelite (calcium tungstate) fluoresce intrinsically in yellow and blue, respectively. When present together in solid solution, energy is transferred from the higher energy tungsten to the lower energy molybdenum, such that fairly low levels of molybdenum are sufficient to cause a yellow emission for scheelite, instead of blue. Low-iron sphalerite (zinc sulfide), fluoresces and phosphoresces in a range of colors, influenced by the presence of various trace impurities.

Crude oil (petroleum) fluoresces in a range of colors, from dull brown for heavy oils and tars through to bright yellowish and bluish white for very light oils and condensates. This phenomenon is used in oil exploration drilling to identify very small amounts of oil in drill cuttings and core samples.



Edited 1 time(s). Last edit at 04/04/2010 03:02PM by Jim Hall.

Hi

I have noted in the past that when a red laser pointer (the type used for lecture purposes) is directed at most Broken Hill (Australia) Smithsonites - particularly the rounded / globular form, that they literally glow a deep pink. Actually makes it easier to discern other asociated minerals that may be lurking on the specimens. I am not sure if this is a real fluoresecence because they don't fluoresce under the usual UV lights. It is as if the Smithsonite is reflecting the laser within itself. It doesn't have to be dark to see the effect - a typical room in softened daylight is ok.

Unfortunately I don't know enough about the physics of Fluorescence to explain what happens or why, or if in fact it is a form of fluorescence or luminescence.

Cheers

Hi Keith,

Have you ever tried other wavelength pointers to see if a similar effect is noticible? Is the glow notably different in hue than the red laser?

Henry Barwood
Troy University
Troy, Alabama USA

Henry, not all Franklin,NJ calcite is uniform in its fluorescence. The general rule is that the Mn range is from just under one % to about 6% above or below this range you tend to get diminishing response to UV sources. The idea is that the farther away from the ore body proper the Mn % diminishes and thus the UV response. There are places in the mine wall rock where you can see this in a linear approach to the ore. There is also variation within the seemingly "uniform" calcite and this is often seen under mid-wave UV light sources. Also some nearby mineral species can quench the fluorescent response from calcite locally referred to as "dead zone" calcite often from secondary intrusive veins.
Perhaps Dick Bostwick can give you a more detailed response. Hope this helps.
Steve.

I haven't tried a different colour laser pointer

My initial reaction was that the light was simply refracting within the specimens - they glow a very intense red/pink - sightly different to the laser red itself. Though this may simply be the fact that the laser is penetrating the translucent Smithsonite. Bit like a red light within an eggshell.

I don't think its fluorescence itself

Keith,

If the scattered light is a different hue than the pointer, then there is likely some fluorescent component. Simple scattering would not alter the hue unless there were selective absorption going on within the smithsonite. Now if the smithsonite is highly colored, that would be a different matter.

Henry Barwood
Troy University
Troy, Alabama USA

Steven,

I know there is a lot of variation in the Mn content of the calcite, I just never realized how patchy it is until I played around with the pointer.

Henry Barwood
Troy University
Troy, Alabama USA

Well, it's rather cool at night when at a locality with lots of orange fluorescing calcite, especially the phosphorescence. And the scorpions are almost too brightly glowing to look at, ha ha.

well just tested several calcite specimens from different localities with a 405 nm laser for response
1. massive pink calcite from Selleck road tremolite locale in St. lawrence co. has response, but none under lw UV. seems odd
2. Yellow Lake roadcut calcite St. lawrence co. New york really bright response, have not tested with lw UV.
3. Thompson-Mckulley qy. Michigan no response.
4. massive calcite from Herkimer New york no response.
5. several calcites from Lockport Formation no response.
6. massive Calcite from Douglas lake in Tennessee no Response to laser but really bright orange response to lw UV.
the first and the last are interesting to me since the responses to the laser and the UV are opposites seems counter intuitive

... calcite from Bösenbrunn, Oelsnitz, Vogtland, Saxony, Germany (405 nm)

Henry,
405 nm is the strongest absorption band of Sm³⁺, which is a strong activator of photoluminescence (PL) in many minerals, e.g. apatite and leucophanite. Often minerals that shows Mn²⁺ luminescence with high-energy excitation (like cathodoluminescence) will actually have REE³⁺ activated luminescence in PL. So perhaps Sm can explain the emissions in some of the calcites.

Berthold,
That is an amazing picture

cheers

Henrik

my Durango Apatite also fluoresces a nice warm orange

Hi Donald,

Attached is a photoluminescence spectra of five different apatites I ran some years back with 405 nm excitation. The sample "DUR" is from Durango. The emissions are from Sm³⁺

Henrik



Edited 1 time(s). Last edit at 10/18/2010 07:06AM by Henrik Friis.

thanks Henrik, very interesting explains why most minerals excited by 405 nm have a similar response. one calcite I tested did have a bright yellow fluorescence and no phosphorescence. I wonder if this would have any practical use aside from the "neat glow".