phosphorescent character in uranium mineral?

[jennifercindrich]

I want to thank you ahead of time for any help or suggestions!!

I was wondering if anybody knew if there was a particular uranium mineral that has the quality of a very bright and long (6 seconds) phosphorescent characteristic?

I am questioning a possible uranium mineral with this quality. I use an UV systems SW super bright III. But It does this also with my cheap LW.

Let me also add that it fluoresces yellow under SW (using a Super Bright III) and LW and it Phosphoreces bright Greenish yellow.The colors in the third photo are not good and should show a lemon yellow and the phosphorescent should show a bright yellow green. My apologies.

The mineral in question forms a crust on calcite/dolomite. (see photo) I am in the Llano Uplift region in Central Texas.

[Alcest]

Hi,

can you specify "Llano Uplift region"? Do you have any name of the mine/quarry the specimen comes from?

Google "didn't find" any informations concerning phosphorescent Uranium minerals.

Are you sure it's a U-mineral? Is it radioactive? A few Carbonates, Sulfates or Zn-minerals are known for phosphorescence.

[jennifercindrich]

This is a newly discovered close-to-surface occurence on my property.

Here is information links to the district Llano uplift--https://en.m.wikipedia.org/wiki/Llano_Uplift
https://www.mindat.org/loc-9986.html

 I am not yet able to test the radioactivity but I doubt that a geiger counter will give a reasonable result, because the amount is so tiny that the radiation would hardly exceede the background radiation. I am already looking for a possibility to test it with a sczintilation device to get a spectrum that will prove (or not) uranium. Which is the exact reason for my question.

[Alcest]

How 'large' are the specimens? Most geiger counters should give noticeable results if it's a U-mineral.

[jennifercindrich]

The specimen shown above is about the size of a sand grain.

[jennifercindrich]

I also have moltened a soft red and malleable metal bead from a different (non-fluorescent) yellow stuff. It gives me reason to think there is no other possibility than bismuth. I have seen some similarities to the Erzgebirge occurences, and thus, I think the Mineralienatlas is a good place for the aforementioned question.

[Alcest]

Well, a sand grain is indeed too small for most geiger counters.

The yellowish stuff you melted could be Bismite.

Be careful once you smell garlic in bismuth-cobalt-nickel associations. Arsenic is a very common element in those and the 'odor' of garlic really isn't a healthy thing.

[Lynx]

Hi Jennifer,

actually I am not aware of a specific uranium-containing mineral with characteristic persistent luminescence. Yet, there might be a few minerals capable of persistent luminescence with uranyl-ions as activators. Calcite, gypsum or fluorite might show persistent luminescence with uranyl ions as activators  - but as well other species.
The origin of persistent luminescence is linked to trap-states in the electronic structure of the material. Charge-carriers induced by illumination with e.g. UV-light  get trapped and are slowly released by thermal energy at room temperature. Heating the material will lead to thermoluminescence.
For such a process to appear the material must allow for luminescence centers (activators) with a ground state - conduction band distance in the order of the energy of the exciting ligh (i.e. electrons are excited into the conduction band) and posess shallow trap states (i.e. stimulable by thermal energy at room temperature): this is a quite generic mechanism compatible to quite a handfull of minerals. If you look in literature you might search for "persistent luminescence", "afterglow", "phosphorescence", or similar.

My excuses for being of little help with respect to your initial question.
In case you are interested in more details or need some literature feel free to ask...

All the best, Martin