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Jesse Fisher
Joined: 18 Mar 2009
Posts: 629
Location: San Francisco
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Posted: Apr 05, 2013 17:58 Post subject: Color and Fluorescence of Weardale Fluorite |
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Most of the fluorite we find at the Rogerley Mine is pretty much a uniform green, but occasionally we find crystals that have distinct yellow zones, usually at one corner of the cube. Weardale fluorite is well known for its strong fluorescence under long wave ultra violet light (LWUV), and recently, while examining some such crystals under LWUV I noticed that the fluorescence of the green portions was much stronger than the yellow.
Intrigued by this, I began a survey of crystals from other local mines that showed internal color zonation. While Weardale fluorite does not, for the most part, show the strong internal color variations seen in fluorite from some other locations (notably, Southern Illinois) internal color bands, often in subtle shades of purple are actually fairly common. The most common colors found in fluorite from the region are various shades of purple, green, yellow/amber, and colorless. I found that the purple and green colors are uniformly more strongly fluorescent than the yellow or colorless varieties, and that the intensity of fluorescence varies with the internal color zones. Some photos of this are below.
Fluorite from the Weardale region is known to have elevated levels of a suite of Rare Earth Elements (REEs), and several authors have speculated that this may be the cause of the intense fluorescence, if not some of the the actual colors. As there looks to be a direct correlation between the intensity of fluorescence and the various colors, it would be interesting to see if there is any correlation between REE levels and the internal color variations in some crystals. Unfortunately, I don't have a microprobe in the basement. Anyone know somebody who does?
Cheers,
Jesse
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Fluorite Rogerley Mine, Weardale, Co. Durham, England 2.5 cm on edge photo on left taken in "daylight-spectrum" fluorescent light, on right in LWUV. |
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20058 Time(s) |
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Fluorite Heights Mine, Weardale, Co. Durham, England 3 cm on edge photo on left taken in "daylight-spectrum" fluorescent light, on right in LWUV. |
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20075 Time(s) |
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Fluorite with calcite Cambokeels Mine, Weardale, Co. Durham, England fov = 5 cm photo on left taken in "daylight-spectrum" fluorescent light, on right in LWUV. |
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20088 Time(s) |
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Fluorite Rotherhope Fell Mine, Alston Moor, Cumbria, England 2.3 cm on edge photo on left taken in "daylight-spectrum" fluorescent light, on right in LWUV. |
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20072 Time(s) |
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Fluorite Stanhope Burn Mine, Weardale, Co. Durham, England 2.4 cm on edge photo on left taken in "daylight-spectrum" fluorescent light, on right in LWUV. |
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20110 Time(s) |
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GneissWare
Joined: 07 Mar 2008
Posts: 1287
Location: California
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Posted: Apr 05, 2013 18:54 Post subject: Re: Color and Fluorescence of Weardale Fluorite |
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Jesse Fisher wrote: | ... it would be interesting to see if there is any correlation between REE levels and the internal color variations in some crystals. Unfortunately, I don't have a microprobe in the basement. Anyone know somebody who does?
Cheers,
Jesse |
George Rossman at Cal-Tech. I will pass along his email address if you don't have it.
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Ru Smith
Joined: 13 Oct 2012
Posts: 362
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Posted: May 01, 2013 22:20 Post subject: Re: Color and Fluorescence of Weardale Fluorite |
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Lovely images, Jesse.
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Mark Ost
Joined: 18 Mar 2013
Posts: 516
Location: Virginia Beach
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Posted: May 02, 2013 17:34 Post subject: Re: Color and Fluorescence of Weardale Fluorite |
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Very nice Jesse. I have several pieces from Rogerley and they are very fluorescent, though the ones I have do not show the zoning so well illustrated in your samples. My Mibladen ones do have nice zoning with two color response. Some night I would like to see how far from one of my English samples I can hold the light and still get a visible response. One has such good response I have gotten it to fluoresce with a prism in the UV end of the spectrum coming out the prism. My Clay Center and Tennessee also have fine zoning. Thanks for the nice photos.
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Mark Ost
Joined: 18 Mar 2013
Posts: 516
Location: Virginia Beach
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Posted: May 02, 2013 17:36 Post subject: Re: Color and Fluorescence of Weardale Fluorite |
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Oh do these patterns reflect fluid changes while the crystal is growing?
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Ru Smith
Joined: 13 Oct 2012
Posts: 362
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Posted: May 04, 2013 22:38 Post subject: Re: Color and Fluorescence of Weardale Fluorite |
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A Hilton example with faint bands.
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Fluorite twin. Hilton Mine, Cumbria, UK. Cube edge is 22 mm long.
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19591 Time(s) |
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ian jones
Joined: 29 Jul 2009
Posts: 112
Location: london
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Posted: May 05, 2013 07:18 Post subject: Re: Color and Fluorescence of Weardale Fluorite |
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Zoned fluorite from the Weardale area is not uncommon. This Boltsburn piece is particularly strongly zoned.
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Fluorite Boltsburn Mine, Rookhope, Co. Durham, UK 56x35x40mm |
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19521 Time(s) |
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Josele
Joined: 10 Apr 2012
Posts: 410
Location: Tarifa, Spain
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Posted: May 06, 2013 13:02 Post subject: Re: Color and Fluorescence of Weardale Fluorite |
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Jesse Fisher wrote: | ... it would be interesting to see if there is any correlation between REE levels and the internal color variations in some crystals. ... |
Fluorite color is a fascinating matter.
As can read in the excelent book "La fluorita" (J.R. García Álvarez et al.), fluorite color can be due, basically, to:
1- color centers (many types) in fluor position.
2- REE elements replacing Ca in the crystal lattice.
3- Calcium coloids in intersticial position.
Some color centers act also as luminiscence emision centers.
Most fluorites due his color to several factors.
Is a long story, please read details in specialized literature.
Hope this can help.
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Fluorite Okorusu Mine, Otjiwarongo District, Otjozondjupa Region, Namibia 11 x 7 x 6 cm Fluorite cubes up to 4 cm with emerald color and lilac in vertex. Under halogen and LW UV. Liliac vertex are less fluorescent than green zones. |
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19432 Time(s) |
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Fluorite Las Monjas geode, La Viesca Mine, Huergo, La Collada mining area, Siero, Asturias, Spain 8 x 5 x 4 cm Zonal colored fluorite cubes on quartz mattress. Purple color can be due to a color center formed by one electron in a F position. Under halogen and LW UV. |
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19480 Time(s) |
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Fluorite Hameda Quarries (Lhamda Mine), Jorf, Er Rachidia Province, Meknès-Tafilalet Region, Morocco 8 x 5 x 5 cm Some well defined yellow fluorite cubes up to 3 cm stand out on massive fluorite. Yellow color use to be due to by replacement of two fluor anions by one O3- anion. Greenish yellow color (like this one) can be due to Y3+ and Ce3+ presence. Under halogen and LW UV. Zonation is more evident in fluorescence. |
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19467 Time(s) |
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_________________ Josele |
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Josele
Joined: 10 Apr 2012
Posts: 410
Location: Tarifa, Spain
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Posted: May 06, 2013 16:39 Post subject: Re: Color and Fluorescence of Weardale Fluorite |
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Only to add that lumuniscence spectroscopy techniques helped to determinate some color centers which act also as luminiscent emission centers, and to recomend a book with exahustive information about this: Luminiscence Spectroscopy of Minerals and Materials, Michael Gaft et al., Springer, 2005.
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Same specimen shown in last photo but here under short wave UV. |
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19398 Time(s) |
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_________________ Josele |
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Ru Smith
Joined: 13 Oct 2012
Posts: 362
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Posted: May 09, 2013 22:50 Post subject: Re: Color and Fluorescence of Weardale Fluorite |
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Excellent information, Josele. Thanks!
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nurbo
Joined: 23 Sep 2008
Posts: 457
Location: Lancashire
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Posted: May 11, 2013 12:36 Post subject: Re: Color and Fluorescence of Weardale Fluorite |
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Here are some more Weardale examples, I especially like the first Blue Circle example.
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Fluorite. Blue Circle Cement Quarry, Eastgate, Weardale, Co Durham, England, UK. 15 mm across longest edge |
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18980 Time(s) |
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Fluorite. Blue Circle Cement Quarry, Eastgate, Weardale, Co Durham, England, UK. 17 mm across longest edge |
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19016 Time(s) |
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Fluorite Allison Pocket, flatt Drift, West Pasture Mine, Stanhope, Weardale, Co Durham, England, UK. Main cube 15 mm on edge |
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18997 Time(s) |
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Fluorite. West Pasture Mine, Stanhope, Weardale, Co Durham, England, UK. 13 mm across the top edge |
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19016 Time(s) |
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Jesse Fisher
Joined: 18 Mar 2009
Posts: 629
Location: San Francisco
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Posted: Jun 29, 2013 14:56 Post subject: Re: Color and Fluorescence of Weardale Fluorite |
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I recently acquired a twinned fluorite crystal from the Boltsburn mine that shows remarkably well developed color zoning for North Pennines fluorite. The LWUV image reveals much more detail than is visible in the normal light image.
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Fluorite Boltsburn Mine, Rookhope, Weardale, England, UK 6 cm across. photos taken in daylight spectrum fluorescent (left) and long wave ultra violet light (right). |
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18343 Time(s) |
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Ru Smith
Joined: 13 Oct 2012
Posts: 362
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Posted: Jul 02, 2013 21:53 Post subject: Re: Color and Fluorescence of Weardale Fluorite |
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Beautiful crystal, Jesse.
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colin robinson
Joined: 29 May 2013
Posts: 82
Location: Cumbria
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Posted: Jul 03, 2013 17:55 Post subject: Re: Color and Fluorescence of Weardale Fluorite |
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That pinkish colour in the Boltsburn crystal is probably the rarest colour to be found in Weardale fluorites. There was a small outcrop in West Newlandside (long gone) and I've seen it from Cambo but, apart from that, nothing. I'd be interested to see which element is responsible.
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Mike Wood
Joined: 16 Dec 2010
Posts: 456
Location: Northern England
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Posted: Apr 12, 2014 05:09 Post subject: Re: Color and Fluorescence of Weardale Fluorite |
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In https://www.mineral-forum.com/message-board/viewtopic.php?p=30335#30335 Jesse Fisher wrote: | ...Fluorite from the Weardale region is known to have elevated levels of a suite of Rare Earth Elements (REEs), and several authors have speculated that this may be the cause of the intense fluorescence, if not some of the the actual colors. As there looks to be a direct correlation between the intensity of fluorescence and the various colors, it would be interesting to see if there is any correlation between REE levels and the internal color variations in some crystals. Unfortunately, I don't have a microprobe in the basement. Anyone know somebody who does?... |
Hi Jesse, I am curious to know if you did get to play with a microprobe on the fluorescent fluorite from Weardale. I have been occasionally fascinated by the different colour banding in the fluorite crystals that are parallel to the faces, and wondered whether they correlate to 'concentrations' of different REE, thus giving differing excitation colours under uv light.
Also, perhaps going into the realms of fantasy here but bear with me: over twenty years ago I wondered whether there was such a thing as a 'tunable uv light source or laser' - ie whether different frequencies of uv light would excite different REE in the banding in the fluorite...Which in turn could be a diagnostic tool for determining specific REE. Imagine a small hand-held tunable laser pen and a colour/identification chart.
Anyone know if there is such a tool these days? Or is it just me? (You don't necessarily have to answer the last question!) ;-)
Cheers, Mike
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