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General'blue spodumene'

9th May 2008 05:53 UTCGreg Dainty

I recently purchased a nice, light blue 15cm D.T.spodumene. Direct from Afgan dealer , here in Australia. After finding no references to blue spodumene in my liturature,I was a bit confused, so decided to do a small experiment, I stuck the crystal in the sun. After 2 hours the color was now that of a nice kunzite, and has stayed that way. I presumme the xl had never been exposed to sunlight , to any real extent , in its travels from the mine to me. What I'd like to know is if anybody else has observed this before in (afghan or any other) spodumene) ? and is there anything written about this particular effect, happening in spodumene?

Greg

9th May 2008 12:58 UTCJim Ferraiolo

Hi Greg,

I extracted this from

Status Report On Gemstones From Afghanistan, by Gary W. Bowersox

on http://www.gems-afghan.com/articles/status.htm

First published in GEMS & GEMOLOGY, Winter, 1985

Spodumene. The spodumene crystals from the Nuristan region are among the finest examples of this mineral ever found. Many details on the pegmatite deposits of spodumene are given in Rossovskiy et al. (1978) and Bariand and Poullen (1978). The transparent, gem-quality spodumene crystals from Nuristan come in a wide range of colors - purple and pink, as well as blue, green, and yellow. Some of these crystals are up to one meter in length. In general, they are well formed, with large, flat crystal faces, relatively sharp edges, a tabular shape, and are often twinned. As with tourmaline, the spodumene crystals are free of any attached minerals at the time they are sold to gem buyers. As is typical of spodumene, which is pleochroic, the crystals from this area display different hues when viewed in different orientations, with the strongest color for light passing parallel to the long direction (c-axis) of the crystal. Dunn (1974) describes some of the crystals as color zoned, but the crystals examined for this paper were more or less of uniform color.

From the study of a parcel of light pink spodumene crystal fragments and several additional faceted stones, refractive indices of 1.659 and 1.677 (±0.003) and specific-gravity values of approximately 3.20 (±0.02) were found. These fragments were pleochroic from brownish pink to pink. No features were visible in the hand spectroscope. When exposed to long-wave ultraviolet radiation, the fragments displayed a strong orangey pink fluorescence. When exposed to short-wave ultraviolet radiation, they exhibited a strong bluish pink fluorescence with a red phosphorescence that lasted for about one minute. When viewed with the microscope, the spodumene fragments revealed three-phase inclusions, growth tubes, and cleavages, and displayed twinning. In general, these properties are identical to those reported for Afghanistan spodumene by Dunn (1974) and Rossovskiy (l981).Most spodumene exhibits the property of tenebrescence, which involves a reversible darkening and lightening of its color with changes in conditions (Claffy, 1953). Pure spodumene is colorless; the various colors (pink, purple, green, yellow) are due to the presence of trace elements such as manganese and iron. Manganese substitutes for silicon, and iron for aluminum, in the spodumene crystal structure. According to Hassan and Labib (1978) and Nassau (1983), a darkening of the color of spodumene to pink or purple (kunzite) can be brought about by exposure to a source of high-energy radiation (gamma or X-rays) that removes an electron from the manganese and changes its oxidation state from 2+ to 3+. Further irradiation produces a coupled oxidation- reduction reaction involving both iron and manganese to turn the pink spodumene green.

Mn3+ + Fe3+ irradiation > Mn4+ + Fe2+

These radiation-induced color changes are thermally unstable, and the color-change sequence described above can be reversed by exposure to daylight, ultraviolet radiation, or moderate heat of a few hundred degrees Celsius. The exact color- alteration behavior of spodumene, and the relative persistence of radiation-induced colors, will vary depending on the nature of the trace elements and the color-treatment history of the stones in question. Because it is colored by chromium, which in spodumene is not susceptible to oxidation or reduction, hiddenite does not exhibit changes in coloration under similar conditions.

When mined, spodumene emerges from the ground with a blue-violet or green color. This suggests that the crystals have been exposed to some natural source of radiation that produced these colors by the mechanism described above. According to the miners, leaving the crystals in the sun for several days, often after having boiled them in water, is sufficient to turn the material to an attractive purple or pink color. Fade tests were conducted to document the thermal stability of the purple kunzite, and determined that heating crystal fragments to temperatures of 4000C for six hours was adequate to entirely bleach the pink color. Exposure of several pieces from a single pink crystal to direct sunlight produced fading to virtually colorless within several days (less than a week). As described above, the pink color can be restored by re-irradiation.

9th May 2008 14:08 UTCGail Spann Manager

I have one hidden away in a drawer to keep it blue, it is just fun to show to the grandchildren and then show them ones in our cabinets that are gorgeous pink/purple.

10th May 2008 09:31 UTCGreg Dainty

Thanks Jim, exactly what I wanted. Gail, I also have another one that I am leaving unexposed,its such an interesting effect. Have you shown the grandkids the pic of Atacarmite after Mouse, that Jolyon posted on a thread last year ?

Greg

10th May 2008 15:07 UTCGail Spann Manager

No Greg, not sure what it is you are talking about. How does one find this photo?

As our eldest grandson would say.." COOOOOOOOOOOOL" !!!!

( 7 1/2 )

10th May 2008 16:35 UTCRobert Knox

Hi Gail... the title of the 'mouse' thread was "One of a Kind Mineral Species and Odd Occurrences of Minerals".

Another sure-fire, child pleasing photo would be one of the opal replaced dinosaur skeleton photos from Australia. I can't remember if one got posted here on the message board, but it is easy to find on line.

Bob Knox

10th May 2008 16:39 UTCGail Spann Manager

Thanks Bob! I will look it up.

4th Jun 2010 10:40 UTCPeter Lyckberg Expert

All the beautiful blue ones comes from a gem pegmatite at Wama.

They are just incredible in color and need to ba protected in a dark box inxide a dark drawer!

5th Jun 2010 03:53 UTCMark & Linda Mahlum

Do you have a picture?

Mark

6th Jun 2010 12:01 UTCRusty James

I heard from my sources that Blue spodumene also occurs in Shigar valley on the Pakistan side, but I don't know if any of it has ever made it to market. Perhaps it fades or changes too fast...

That atacamite after mouse photo made it to the front cover of The Vug's small magazine for the Tucson show a few years back.

9th Jun 2010 20:39 UTCAnonymous User

I saw some spodumenes that came out of Elizabeth R that were almost blue, they had JUST been mucked out and therefore had never seen the sunlight, but I assume they didn't stay that color for long!!

10th Jun 2010 01:00 UTCAdam Kelly

My light blue spodumene lives with my other "kunzites" in a bag, in a bag, in a box, in a drawer.

I have seen dark purple fade to light pink, and electric green fade to milky clear.

AK

3rd Jul 2010 16:37 UTCPeter Lyckberg Expert

Just as a note. There is one pegmatite at Waygal which produces the darkest finest purple kunzites some with blue purple color. If exposed to strong sunlight (which you never should do with kunzite, champagne topaz and many other minersls as discussed in Jordi Fabres forum and I believe also here) the color goes toward a dark ruby red purple. I have never seen this material on the western market though and the material is of such high gem quality and color stable that every bit is rapidly bought by gem dealers and facetted!

9th May 2023 07:42 UTClana gold

Have you tried to turn it blue again? I have 65 ct blue and it went pale pink after 1 minute under sunlight, now I am wondering if it is reversible!

Lana

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