Learning Center What is a mineral?The most common minerals on earth Information for Educators Mindat Articles The Elements The Rock H. Currier Digital Library Geologic Time

Minerals by Properties Minerals by Chemistry Advanced Locality Search Random Mineral Random Locality Search by minID Localities Near Me Search Articles Search Glossary More Search Options

The Mindat Manual Add a New Photo Rate Photos Locality Edit Report Coordinate Completion Report Add Glossary Item

Mining Companies Statistics Users Mineral Museums Clubs & Organizations Mineral Shows & Events The Mindat Directory Device Settings The Mineral Quiz

Photo Search Photo Galleries Search by Color New Photos Today New Photos Yesterday Members' Photo Galleries Past Photo of the Day Gallery Photography

Discussions

💬 Home 🔎 Search 📅 Latest

╳Discussions

💬 Home 🔎 Search 📅 Latest

Groups

Recent Images in Discussions

GeneralDisplaying light-sensitive fluorite

16th Aug 2016 07:03 UTCBrenton Mah

I am aware that fluorite of certain colors (namely colors other than green and purple, particularly blue) can fade in sunlight, but I was wondering if the same can be applied to light emitted from bulbs for display cases and so on. Is it light in general that will fade blue fluorite, or only sunlight? I presume the UV from the sun is the culprit, so that's why I'm wondering if it's safe to display blue fluorite with incandescent bulbs. I'm also wondering if the sensitivity changes for bulbs of different temperatures.

Of course, it's probably safe to not display those fluorites in any sort of light for an extended period of time and just make the assumption that they'll fade in any kind of light. But I'd like to know if this is really the case or not. If I can display them with certain bulbs indefinitely, I'd be quite pleased!

18th Aug 2016 07:32 UTCStephen Moreton Expert

Direct sunlight is certainly bad news for sensitive fluorite. Not sure about artificial light. English green fluorite turns purple after a few months in the sun. I keep mine in the dark and only bring it out on ceremonial occasions. English purple and amber fluorite is stable.

20th Aug 2016 02:40 UTCBrenton Mah

Well that's just it, right? I'd like to know if light altogether is harmful to certain fluorites, or if only certain kinds of lights fade those crystals. Assume sunlight does not reach the artificially-lit display cabinet. Is it ok to leave blue fluorites in that cabinet for weeks?

20th Aug 2016 05:18 UTCAlfredo Petrov Manager

Why not keep them in a dark display case and just turn the lights on intermittently when someone wants to view them?

If the fluorite looks blue, that means there is blue light in the lights you're using to illuminate them, which might not be good. I don't know which wavelengths affect fluorite. It's possible no one has yet done that experiment. We can not automatically assume that it must be the sun's UV light that does the damage. When experiments were done with realgar it was found to be green light that destroyed it. With other minerals, UV is a likely culprit but we can't just assume that that is the case. So darkness is safest.

20th Aug 2016 16:31 UTCJolyon Ralph Founder

also green fluorite is not always safe. Rogerley fluorite turns permanently purple if left in the sun too long.

15th Jun 2018 17:22 UTCFlorian Baur

I bought a Rogerley fluorite that shows strong daylight fluorescence. I thought it wouldn't be that sensitive to UV. To luminesce this strongly, the Eu2+ ions responsible for the luminescence have to absorb quite a lot of the UV light and convert it to blue light. That means a lot of the incident light's energy is emitted again.

also green fluorite is not always safe. Rogerley fluorite turns permanently purple if left in the sun too long.

This doesn't sound too good though. Or is it really only direct outdoors sunlight and indoors indirect sunlight is ok? Does anyone have exprience with long term display of Rogerly fluorites?

And how about shining a 365 UV LED at it? That's a lot stronger than sunlight, so I assume it's something that should be done rarely if at all?

15th Jun 2018 18:53 UTCJolyon Ralph Founder

> direct outdoors sunlight and indoors indirect sunlight is ok?

This is a dangerous thing to debate because it depends on a few things.

Firstly, do we know if it's the UV that's causing the permanent switch to purple, or some other component of sunlight?

And even if it is the UV, do you know for sure your windows are blocking it?

Green fluorite left on the dumps at Rogerley turns purple very quickly, maybe in a few weeks at most.

15th Jun 2018 19:16 UTCMatt Courville

Brenton, perhaps you could use or buy some rough examples of the particular blue fluorite which you are asking about. They should be cheap if they are massive or busted-up crystals. Then set-up a series of tests, over time, and with variables.

Eg:

5 min, 10 min, 30 min, 1 hr, 5 hrs, 24 hrs, 2 days, etc. and then have each under different light sources - daylight, UV light, and various home bulb options. I would start it on a day which has decent sun. Post what you find;)

I've seen blue fluorite from Madoc, ON fade rather quickly, but strangely enough are visually far more vibrant blue in the sunlight than when under artificial lighting in my house. Also there are two colors of fluorite found at the Beryl Pit locality in ON by which one stays a purple color regardless, and the other fades from raspberry to clear in a matter of hours.

I would say each locality and each color itself would require this sort of approach. It would be rough to ruin a good fluorite;)

15th Jun 2018 23:12 UTCScott Rider

I have had many fluorites on display, yet, they were purple and green specimens. I have my rare stuff in boxes packed away, so I inadvertently kept them safe, like Swiss pink fluorites, blue cubes from Lake George, etc.... Good to know.

16th Jun 2018 04:51 UTCJim Allen

I have a Blanchard Mine blue fluorite that sat on a display shelf, out of direct sunlight, for 30 years without losing color. It had no artificial illumination, but wasn't protected in any way, either.

16th Jun 2018 15:48 UTCDouglas Merson 🌟 Expert

I have a French fluorite that was a very nice pale blue. It was in a case that had no direct sunlight. It is now an ugly pale grayish green. The room lighting varied from incandescent to compact fluorescent to LED. The case lighting is four 4 foot tubes that are the equivalent of OTT lights. Just the occasional use of those lights is the likely cause of the fading.

None of the other fluorite specimens in the case have been affected and they are various colors from a number of locations.

17th Jun 2018 02:03 UTCKeith Compton 🌟 Manager

From memory, Jesse Fischer and co had a good article on the cause (rare earth minerals) of Weardale fluorites and colour change in daylight and different lightiing conditions.

Unfortunately I don't have a copy , and their website doesn't seem to exist anymore.

17th Jun 2018 15:04 UTCKevin Conroy Manager

Keith, is this the one that you were thinking of: http://www.mineraltown.com/Reports/24/24.php

Related, and a bit more technical: summit.sfu.ca/system/files/iritems1/17481/etd10231_SMakin.pdf

17th Jun 2018 15:50 UTCTony Albini

Hi Brenton,

When I lived in Connecticut, USA, Old Mine Park in Trumbull, CT had multiple hydrothermal veins with tungsten minerals, or topaz, or fluorite mineralization. Fluorite, variety chlorophane, was found as masses of red, pink, and colorless material in the cut and dump. I read about villiaumite, which occurs in nature as pink and and I think red material. When synthesized, it is colorless. At least one author claims the color of the natural villiaumite is due to a structural defect in the NaF molecule. My observations in the field seem to indicate that the fresh fluorite starts out as red materal, fades to pink and then colorless with no blue green fluorescense as with the red and pink material. I keep my pink material in a box and as Alfredo Petrov suggested, just take it out to show people and I use the same piece for FL use. I hope you find this information useful.

17th Jun 2018 23:58 UTCKeith Compton 🌟 Manager

Kevin

No there was a very detailed article on REE and effects with Rogerley fluorite.

Cheers

21st Jun 2018 18:14 UTCFlorian Baur

The blue emission is Eu2+, the green color though has to have another cause as Eu2+ in CaF2 absorbs UV light, but not red. I think I read Rogerley green fluorites (or green fluorites in general) are colored by Fe2+, and the Eu2+ was somehow connected to its formation or stabilization.

Firstly, do we know if it's the UV that's causing the permanent switch to purple, or some other component of sunlight?

You're right, as it's green there should be absorption in the red, so it might even be that.

And even if it is the UV, do you know for sure your windows are blocking it?

Not completely, that's true. UV-C and UV-B are absorbed, but UV-A goes through.

Green fluorite left on the dumps at Rogerley turns purple very quickly, maybe in a few weeks at most.

That seems to settle it. I'll also ask the seller (Spirifer) I think they did some collecting themselves so they should know. :)

Mindat.org is an outreach project of the Hudson Institute of Mineralogy, a 501(c)(3) not-for-profit organization.
Copyright © mindat.org and the Hudson Institute of Mineralogy 1993-2024, except where stated. Most political location boundaries are © OpenStreetMap contributors. Mindat.org relies on the contributions of thousands of members and supporters. Founded in 2000 by Jolyon Ralph.
Privacy Policy - Terms & Conditions - Contact Us / DMCA issues - Report a bug/vulnerability Current server date and time: April 25, 2024 14:24:16

Go to top of page