Crystals That Phosphoresce Under Blue (405nm) Laser Only

[AlbertD]

I got one of those $8 China specials off of E-Bay. Pot-modded it to about 100mw. Starts a match almost instantaneously. Been using it for for several months now. I only let it cool down when the barrel shows signs of becoming warm.

I explored my rock-shop with it, wondering if I might spot some fluorescent rocks and minerals I had overlooked before. Well, none of them showed signs of fluorescing. But as I was leaving my shop I accidentally swiped the laser over a crystal cluster that I had previously tested under long-wave and short-wave UV light. It showing no signs of any fluorescence nor phosphorescence before so I didn't bother intentionally checking it with the laser. I noticed something immediately odd. It left a streak of bright magenta phosphorescence that lasted about 1/4th second.

Here's some photos (taken from a short video) to show the trail left behind the laser as it was played on the crystals. It starts out as the bright magenta as seen by the eye, but then rapidly turns into a bright orange. In some of the video frames there were areas that also dimmed into deep reds too but that was more rare.

And a short animation from the last frames of video used to capture the above frames. The 30 frames per second slowed down so you can count how long the phosphorescence lasts, anywhere from 7 to 8 frames. My initial estimation pretty much right on the mark.

I'm guessing that the extra bright intensity of this blue laser is what finally reveals this phosphorescence that does not show up under any UV lights that I've used on it.

I think a blue laser should be a new testing tool for any rock-hound. If my mineral identification guides included an entry on each mineral of its effects under blue laser, it would be much easier to identify these light, grayish-white, translucent crystals (hardness, less than a pocket-knife blade, 2 angles of cleaveage or growth, at 90 degrees and another at 60 degrees).

If anyone knows what minerals (crystals) react this way under blue laser, feel free to post the answer.

If these are the only crystals ever known to do this, expect an outrageous bidding war on E-Bay sometime. :yh:

(btw: this laser pointer forum is anything but dial-up friendly. It takes about 6 minutes for me to download 1 meg on my dialup. Just the main page is over 3 megs full of uncompressed ad images. I go and do something else while waiting for it to finish before I can finally log on.)

 

[Ramsey_innovations]

Re: Crystals That Phosphoresce Under Blue Laser Only

What is the wavelength of the laser you are using and calling "blue"? I've had citrine crystals fluoresce with a 405nm U.V. laser before.

 

[AlbertD]

I edited the subject to say the frequency. 405nm. I guess that's considered a violet laser then?

This isn't fluorescent. They're only phosphorescent. There is no color change of the laser while it is held in one spot on the crystals (other than, I presume a slight whitening effect from the phosphorescence beneath it). It still appears like the normal violet-blue color. It is only when the laser is moved rapidly to the side that the dimmer short-duration magenta to orange (sometimes red) phosphorescence where the laser was striking becomes visible for only 1/4th second.

 

[Ramsey_innovations]

phosphoresce, you would be correct, not fluoresce. What I have see is the exact same thing your pictures are showing and it was definitely citrine. It leaves short trails of orange/red. Oh, and thanks for clearing up the wavelength question we like to be specific around here when it comes to light. Welcome to the forum it's a great source of knowledge.:beer:

 

[AlbertD]

Interesting about the Citrine. But this couldn't be that. They are far too soft. A pocket-knife blade (hardness 5.5) easily causes deep scratches in it. Citrine is a quartz at hardness 7. I'm guessing this might be a form of Calcite (hardness 3) and with the growth or cleavage planes having both 90 and 60 degree angles. Difficult to determine which, because this is a large conglomerate mass with no protruding points. My mineral ID skills are rusty and my lab is in storage so ... But thanks for the further input. It's interesting that other minerals exhibit the very same short duration phosphorescent effect. I'm hoping that maybe someday mineral ID guides might include a "405nm laser test" entry to make ID-ing these things even easier. Every bit of extra clues can help.

If nothing else, this might encourage others to explore the rocks and minerals in their areas to discover new things, lead them into new interests or adventures.

p.s. A heads-up warning for those wanting to photograph effects by laser. A laser can and will instantly destroy the photosites on a sensor in a digital camera. BE CAREFUL. When photographing crystals such as this, make certain that any and all reflecting faces on crystals or other items will not reflect the laser beam directly back into the camera lens. Or you might just end up with a permanently ruined sensor with streaks in every image. I did the above images with this in mind, so my camera was perfectly fine afterward.

 

[Wallydraigle]

I have a couple opals that mildly phosphoresce. Some diamonds will do it too, but the ones that do are clearly fluorescent.

 

[qumefox]

Which $8 china special did you get? None of the cheap chinese 405 pens i've played with so far have drivers capable of more than 85mA, which puts the output at 50mW according to the LPM. In my digging on these pens, I discovered that there are no less than four chinese manufactures making them that all use the same outer casing and labels. Just wonder which seller you got yours from so I could try another batch and see if they had different drivers.

And btw, the vinyl tiles on my kitchen floor are phosphorescent under 405. I haven't really noticed anything else in the house or outside that is though. Most stuff I find just fluoresces.

 

[AlbertD]

Looking back on my e-receipts, I got mine from a seller going by the handle of "tobelieveus" on March 30th. For $0.99 with $7.95 shipping. Okay, not quite $8, but you wouldn't have believed me telling you it was only 99 cents.

I don't like disassembling the green and 405nm lasers I've gotten, so I pot-mod them by measuring the distance from the back of the opened host assembly (using a toothpick as a depth gauge) to where the pot is located on either side of the circuit board. Then I use a tiny ball-shape dremmel rasp to cautiously pierce a hole above where the pot resides. When drilled from the side like that, the shaft of the rasp prevents me from accidentally going too deep and hitting the circuit board. Adjusting the pot with a small nylon screwdriver (often sold for adjusting RF coils). Using the "tested" or "warning" label to later cover up the hole.

Interesting. I checked on ebay just now to see if "tobelieveus" was out of China or Hong Kong, and it comes up as "no longer a registered user". Maybe they were undercutting others' prices just a little too low to try to grab their share of the market and realized it was a loss for them.

FWIW, the pot on this circuit board (if looking at the switch, with the laser output pointing away from you) is on the switch side of the circuit board and centered 2mm to the right of the center of the switch button, and 4mm forward of the center of the switch button. Does that help to let you know if it's one of the models you've tested?

Considering that this 405nm laser will light a match almost instantaneously (as opposed to my pot-modded green lasers which might take one or two seconds), I'm only guessing at the ~100mw output.

 

[qumefox]

That's a different driver than the pens i've checked so far. All of mine have had the pot on the bottom of the driver, opposite of the switch, so i'm not surprised it's a different driver. I wasn't trying to argue the power issue. I know all too well chinese manufacturers tend to change parts sometimes daily going from vendor to vendor trying to keep costs minimal. I was just trying to find another source for my next batch for experimentation purposes. What you say fits pretty well with what i've read of the 'old' 405 pens (ala, a few months ago) having drivers that maxed out around 200ma, where now, they seem to have gone to cheaper ones that max at less than half the current.

 

[itw3ak]

Nice!, probably Calcite I have a couple of pieces that behave just like that under the 405nm light. Hard to find one that will hold that "charge" for very long though. FYI if you ever get a chance to visit the natural history museum in Washington D.C. check out the gems and minerals exhibit and look for the calcite and try a 405nm pointer on those! Its quite impressive! They have a lot of specimens that fluoresce and phosphoresce too.

 

[sarbanes]

Melatonin behaves similarly, and is one way you can test for it's presence. The half life of the electron fall back is very short ~.2 seconds, but you can notice it. I wonder weather it might be possible to use 405nm as a pump, and shoot through some artificial crystal to come up with a new visible wavelength/color?

 

[AlbertD]

@itw3ak: That was my first instinct too, some form of calcite. And on further inspection this morning, I don't know where I got that 90-degree cleavage plane from, this is definitely rhombohedral. Since there are no clear projecting points in this haphazard mass it was difficult to easily spot the angles. I finally found some planes looking very much like a chunk of Icelandic Spar that I use to demonstrate double-refraction. Only this is more opaque to semi-translucent, light grayish-white with a few pinkish inclusions in some of the crystalline structure.

I found it interesting that if you just walk down any old dirt and gravel road with a short-wave or long-wave UV light in hand, you can usually spot a few fluorescent forms of calcite. They will generally only look a little lighter than everything else awash by the violet glow, like a dim creamy-white. The interesting thing is that many of these will exhibit a very very dim, long-duration, orange, yellow, or greenish-yellow phosphorescence that lasts many minutes to the fully dark-adapted eye. Visible only in a totally dark room, or during a cloudy night in the countryside. Starlight can sometimes be brighter than their phosphorescence. They won't show their color very long, but your B&W receptors will still be able to detect the glow.

If that Gems and Minerals display you are talking about is the one at the Smithsonian, then yes I have been there. Some amazing mineral and crystal specimens on display. A "must see" when there. My visit was long before there were any solid-state 405nm lasers to carry in a pocket. Even before red ones. HeNe lasers were just getting popular back then. (I still have a small HeNe fashioned into a "toy death-ray" powered with a stack of 9V batteries in the hand-grip. )

Trying to ID this danged thing is restarting some old brain-cells. Been on the search for some mineral ID software (free if possible) and found some interesting sites online that I didn't know existed before, like Mineralogy Database - Mineral Collecting, Localities, Mineral Photos and Data It's been years since I've done some serious rock-hounding. This 405nm laser might get me out in the quarries and fields again. I even went and ordered a 395-405nm "UV" 12-LED flashlight from ebay last night ($3.64 w/ shipping, cool deal), thinking it might be brighter than my other portable UV lamps that I used to use. Found a nice 3W LED headlamp for night-hiking too for only $3.29. Those suckers used to cost over $90 not long ago. I'm thinking I might even rig up a small Fresnel lens in front of it so I can focus it like a spotlight. Sorry, rambling off-topic here. I have a "nothing else to do" moment on my hands.

p.s. @qumefox: Thanks for the info about those drivers. I guess I happened to buy one at the right time during the Blue-Laser-Pointer Price-Wars. I love when that happens. A similar thing happened for my GPS too. Bought a close-out special that has the best chipset combo of both older and newer models released during that turn-over point in manufacturing. I've not found any consumer-level GPS yet that can beat its accuracy and performance. Newer is not always better these days. I'll keep this in mind about this 405nm laser. Being more cautious to not burn it out because it can't be inexpensively replaced,. Though it seems rather durable during all these months of use, even when cranked that high.

 

[qumefox]

I wouldn't worry too much about it. If your decent with soldering.... and can get the pen apart without tearing the driver up, you can just replace the diode with a PHR if it ever dies. ~100mw of 405 wouldn't really break the bank either even if you had to get one from one of the reputable manufacturers.

Makes me wish I lived somewhere more interesting. The only rocks you'll find around here would be on gravel roads. Everything else is flat and green.

 

[AlbertD]

I wouldn't say that the people I bought this laser from were not reputable. Just because it was inexpensive doesn't mean it is not good or prone to burn out. Especially if I ran it at the specs it was originally sold at. Expensive ones burn out just as well. In today's day and age, the old adage "you get what you pay for" no longer holds true and hasn't for a long long time. All that saying does is make greedy people wealthier.

I also wouldn't say you lived in an uninteresting area of the country. Tennessee is one of the richer areas for caves and unique rocks and minerals. You must have skipped my paragraph too about gravel roads. That's where I found some of the more interesting phosphorescent calcite specimens, in nearly every part of N. America.

 

[qumefox]

I didn't really mean reputable as in scammers. I was just referring to the more well known laser companies that have known good quality. CNI, O-like, etc.

Actually 'you get what you pay for' very much applies to cheap high powered lasers, but not really cheap low powered lasers. Most low power ebay lasers are going to be overspec, and the high power ones are going to be way under spec and/or die quick.

Your right about TN... if your talking about east TN. I however live on the other end of the state. There isn't a cave around here for 300 miles at least. Everything here is flat mississippi river basin type land.