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Fading fluorite.
  
  Index -> Conserving, Preparing and Cleaning Minerals
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vic rzonca




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PostPosted: May 02, 2016 17:50    Post subject: Fading fluorite.  

Simple question, I think. Does fluorite fade in sun light?
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Linus




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PostPosted: May 02, 2016 18:16    Post subject: Re: Fading fluorite.  

Yes, indeed. Almost all fluorite is extremely susceptible to sunlight, some colors fade slower than others, but they all fade. The effect also happens under normal halogen light, but I suspect it is much reduced under LED. - then again it may just take longer to fade...
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Bob Harman




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PostPosted: May 02, 2016 18:46    Post subject: Re: Fading fluorite.  

I agree fluorite does indeed fade from sunlight. The blue fluorite from Bingham, New Mexico goes from pleasing shades of blue to dingy light grayish white after just a few years of being kept in sunlit areas. CHEERS.....BOB
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alfredo
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PostPosted: May 02, 2016 19:33    Post subject: Re: Fading fluorite.  

A dealer in Arizona imported a large quantity of deep purple fluorite from Mexico; such a dark purple that it looked almost black and would not have been easily saleable. He put it up on the roof of his warehouse, exposed to the intense desert sunshine, for six months, which bleached it to a nice transparent violet. The trick of course is not to forget it and leave it in the sun too long!
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Jesse Fisher




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PostPosted: May 02, 2016 20:32    Post subject: Re: Fading fluorite.  

To my experience, the color stability of fluorite can vary widely between locations. As mentioned, the blues from Blanchard Mine are known to fade fairly quickly with exposure to direct sunlight, while fluorites from Southern Illinois seem fairly stable. Weardale greens from mines such as Heights, Rogerley, Eastgate Cement quarry and West Pasture are all unstable, though the exposure time required to bleach them can vary between locations from a few weeks to a year or more. Purple fluorite from Weardale appears quite stable, and I have picked up fragments off dumps that have been in existence for over 100 years that still resemble newly mined material. One unusual occurrence I recently noticed is some pale dishwater yellow fluorite I collected from a minor cross vein at the Rogerley a few years back. I left a piece as decoration on a window ledge that gets several hours sunlight a day and after about six months noticed that it had darkened considerably. Below is a photo of two pieces, the one from the window on the left and an unexposed piece on the right.


IMG_2001r.jpg
 Mineral: fluorite
 Locality:
Rogerley Mine, Sutcliffe Vein, Frosterley, Weardale, North Pennines Orefield, County Durham, England, United Kingdom
 Dimensions: 12 cm (larger piece)
 Description:
darkening of color due to exposure to direct sunlight in fluorite from the Sutcliffe Vein, Rogerley Quarry
 Viewed:  4808 Time(s)

IMG_2001r.jpg


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Jamison Brizendine




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PostPosted: May 12, 2016 11:28    Post subject: Re: Fading fluorite.  

I remember a dealer telling me when I first started collecting there was another dealer that bought a few flats of inexpensive Bingham, NM fluorite. He would then take the fluorite, cover portions with masking tape, and then leave them in the sun to "bleach". Afterwards he would remove the masking tape and as a result you had specimens with bands of blue/purple cubes and bands of grey cubes. The high school that I taught at in Indiana had one of these specimens.
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