Hello! Does anyone know how the phenomenon of blue spodumene fading to colourless when exposed to sunlight? But what is in the sunlight to cause it to fade? Is it both the UVA and UVB radiation, or is it the colour of the radiation (green light or red light)? Is it just sunlight, or any lighting that would cause spodumene to fade?
I hope to hear an answer from someone who can answer this question. Please be as detailed as possible; the more scientific information, the better.
Thank you!
Blue Spodumene is sensitive to the UV spectrum. The material is more reactive to the shortwave spectrum (UVB) centered around 254nm versus the longwave (UVA) between 320 - 400 nm. Since natural sunlight contains UV, it can damage the optical properties at a slower rate.
I may not be able to articulate my understanding of the phenomena with true brevityā¦ but here we go:
There are two related phenomena:
Photochromism - āThe permanent change in optical properties to a crystal lattice, at the molecular level, due to the effect of ionization from electromagnetic or higher energy radiation sources.ā
Tenebrescence - āThe temporary or reversable change in optical properties to a crystal lattice, at the molecular level, due to the effect of ionization from electromagnetic or higher energy radiation sources.ā
The stage: Some crystal lattice structures are inherently weaker than others based on the type of crystal system and the associated internal bonding points at the atomic level. This is evident with the durability and hardness a gemstone displays.
The interaction: As light passes by an atom in a crystal lattice, its vibrational energy can transfer energy into the valence electron shells. The natural resonance for a particular element or molecule will have a fundamental frequency and several harmonic orders. The magnitude of the interaction of the light and crystal lattice is observable as emission or absorption lines in a spectroscopic scan or image. Impurities or trace elements are commonly present providing the distinctive colors we observe visually and identified spectroscopically. The crystal lattice can contribute or generate the natural hues we see visually based on the optical properties.
The effect: The energy transfer from the light to the crystalās atomic structure can cause a bond point to break or change its alignment with an adjacent atom or molecule chain. The natural resonance frequency will change. When this occurs, the visible spectrum we observe will change.
Interesting fact: It is understood that natural blue spodumene develops its visible color hue and saturation while in close proximity to radioactive minerals in the local matrix during its crystal growth. There has been some experiments attempting to recover the natural color hues in spodumene using irradiation treatments. The effects are short-lived and not permanent.
The following link has some excellent literature that dives deeper into the fundamentals, that I poorly attempted to dialog here. I recommend reading chapters 5, 10 and 11; but the entire text book is worth studying and retaining as a resource.
https://opengeology.org/Mineralogy/
-Cheers!
Troy
Thank you, TroyJ49412! I would like to ask you one more question: I do have several large radioactive gemstones, a 12.30 ct and a 7 ct bastnƤsite, 8.30 ct ekanite, and a 3.14 ct thorogummite. If I store the blue spodumene in the same container has all of these radioactive gemstones, and if I give enough time (like several days or weeks), will there be enough radiation to change the colour of the spodumene to blue (if it ever became colourless)?
In other words, will the radiation āre-chargeā the crystal lattice so we see the original, blue colour of the blue spodumene, if the spodumene was to ever fade? Could the radiation be used to retain the blue colour?
I hope to hear from you soon. Thank you!
Hi Thomas,
I cannot give a good answer to how much exposure time the spodumene would need to receive from the stones you have described. Keep in mind, the natural process took place over several millions of years. We do not understand what level or type of radiation the crystal was exposed to during its development. Nor can we be certain other factors didnāt contribute, such as pressure and/or temperature.
Your āspicyā gemstones may not have enough radioactivity to re-align the atomic structure in the spodumene in a few short weeksā¦ I suspect, it would be a similar time-frame as the original development. I donāt know about you, but that is definitely too long for my expected attention span. 
The irradiation experiments I mentioned had very poor results. The return of the coloration was temporary and disappeared in a relatively short time. The UV damage to the crystal lattice is effectively unrepairable. Those experiments used a very, very āspicyā source, like Cobalt60. Which is a highly monitored and controlled material.
Also, I recommend you compartmentalize (physically shield) the radioactive gemstones from each other (if you havenāt done so, already). They can influence each othersā decay rate, which could make them āmoreā spicy over time and elevate their potential health risk.
Cheers!
-Troy
Okay, Troy. Yes, the radioactive gemstones are separated in lead pigs. Okay, thank you for the response!
I plan on wearing the blue spodumene in a setting, as a pendant; the blue spodumene is going to have a piece of coated UV resistant sapphire glass cabbed over the blue spodumene, fixed as a sit in the pendant. Itās so I can wear the blue spodumene outside in sunlight, without worrying about the degradation.
What do you think about this? Do you think it would work to prevent / rapidly slow down the gemstone from fading?
I hope to hear from you soon. Thank you!
A person said:
That is a novel idea! They are commonly called āevening stonesā, as they are usually worn in evening and night time settings only.
I believe a UV blocking barrier should help protect the spodumene. Not sure you need to use sapphire glass, though. That maybe more expensive than the spodumene itself and make the overall pendant heavier.
Are you only going to cover one surface? Will there be any risk to exposure from the sides and back? something to considerā¦
No matter what you choose as a barrier material, there are several coating types out there, so it would be good to use one that protects against both types of UV.
I responded:
The sapphire glass is going to cover the top face of the gemstone only, and the Ytterbium metal will be the setting, and cover the rest of the gemstone. The gemstone will sit in the setting, with the front to sit right behind the transparent sapphire glass (that will be tinted with UV resistant coating (UVA and UBV), to show the grand display.
Hopefully it will workā¦
Thank you, (person who said the above comment).
put simplistically, as I know only a little of quantum mechanics, Mn+2 in spodumene is subject to crystal field splittingā¦ the lattice crystal field energy splits out energy levels in the outer degenerate d orbitals allowing for a bigger jump in energy when the ions interact with visible and UV lightā¦ exposure to UV, radiation and heat can oxidize Mn+2 to Mn+3ā¦ causing loss of colorā¦ more importantly is damage to the crystal latticeā¦dislocations and other defects in the lattice will change field splitting energies or nullify the effect, leading to loss of colorā¦ Spodumene is an unusual pyroxene in that lithium which is of very light atomic weight is more mobile and less strongly bound to silica tetrahedra, has a lower vibrational energy than common iron/ magnesium/calcium pyroxenes, thus making it more susceptible to lattice damage than mafic pyroxenes. Colored beryls are more color fastā¦ Be+2 has half the size of the ionic radius of Li+1ā¦ the charge density is much higherā¦making for stronger ionic bonding, and lattice stabilization.
Aluminum substitutes for silicon on the Z site of the silica tetrahedraā¦ which also accomodates smaller ions, including transition metals, and lithium and sodium. general formula is XY (Si,Al,)2 06ā¦mafic pyroxenes have less Al, or none, with iron, calcium and magnesium being in solid solution with each otherā¦both jadeite and spodumene minerals are derive from alkalic conditions and are intermediate in silica saturation between albite and nepheline. Donāt know whether this makes sense, but thatās my take on it. I should mention that jadeite is a metamorphic mineral that developes under blue schist faciesā¦ high pressure, low temperatureā¦ Spodumene is a low pressure, low magmatic temperature/hydrothermal mineral found in pegmatites.