How much of a problem (if any) have you all experienced with
Kunzite fading over time with exposure to UV light? I have a
customer who wants to purchase a large piece of the pink
spudomene and have it set into a ring. I am trying to convince
this collector to buy it but keep in unmounted in her collection
because of my fear of its fading. How valid is this concern? Has
anyone seen any authoritative articles on the subject?
Thanks!
Shari V @ Vanguard
It’s a very valid concern. Fading in Kunzite is not something
that occurs only some of the time. ALL of it is subject to this
effect. It doesn’t happen instantly, but if worn outside a lot,
it will fade fairly quickly. Brief exposures won’t do much.
Also, Kunzite (a spodumene) has one direction of perfect and
easily developed cleavage, which means the stone is at least a
bit fragile, especially in the setting process. The answer is
simple. Set the stone in Platinum, to begin with, as it’s
chances of surviving the setting process with platinum are much
much better. Side stones or decorative devices that would help
sheild the stone from accidental impacts are also useful. Then,
advise your customer that this is a ring intended ONLY for
evening wear. They fade when they get hot, or are exposed to
U.V. Once the sun is down, ordinary wear out on the town, or to
the theater, or indoors in general won’t hurt it. Owned with
knowledge of it’s limits, and worn with the care it needs, it
can last a very long time in fine jewelry. But it really does
need that awareness and care.
Peter Rowe
To begin with, Kunzite is a relatively soft stone (hardness 6 -
7). I always try to discourage Kunzite for rings. Especially
for a “collectible” stone. Secondly, Kunzite WILL fade
(irreversably) in time if exposed to sunlight.
Kunzite has different color intensities depending on the
orientation. The pink is more intense when viewed along the
c-axis of the crystal. Pale pieces that came from an originally
intense rough may simply have been cut so that the main view was
along a different axis, and may not be faded. Whether fading
does occur as well, I can’t answer.
Tas
I have a Kunzite in my display case that has been exposed to
showroom lighting (halogen) but not direct sunlight. I would say
it has lightened by about 50% over a 6 year period. According to
Kurt Nassau, author of “Gemstone Enhancement” light will cause
some Kunzite to fade. He also describes methods for changing the
color of kunzite, most of which are very temporary.
Steve Howard
Hi Shari: In all I have seen, Kunzite fades if in
direct sunlight for hours. It is also subject to chipping. Just
tell the customer that she cannot sit in the sun with it and it
should be fine! Sincerely
chris
http://www.tace.com/glitters
Buying and Selling Fine Jewelry, Antiques and Collectibles
Unfortunately, I don’t have much experience working with
platinum. Could you enlighten me? Why would the Kunzite have a
"much, much better chance of surviving the setting process" if
set in platinum? If it’s a harder metal, won’t it take more
applied pressure to set it? Also, it’s a large stone, so the
cost in plat. may be prohibitive.
Thanks for your help…
Shari VanderWerf @ Vanguard
I missed the part of the thread that talked about setting the
stone in platinum but there are two issues here. The first is
that the hardness of platinum doesn’t refer to it’s malleability
which is what you actually are using when setting the stone. But
the second is that I have found setting any stone in platinum
(even pure plat which I use sometimes) is more difficult than
setting in a higher karat gold. My advice to anyone trying to
set delicate stones is always to use the highest karat gold
possible. We regularly use 22k for our settings. It is much
easier setting any stone in that. On the other hand if you need
a white metal for the ring I would recommend Hoover and Strong’s
18k palladium white gold, although I find even that tends to be a
little springy when setting.
The actual surface hardness, or bending resistance of platinum
is NOT harder than white golds. But it makes, when properly
done, a longer wearing, safer prong. Among other things,
platinum is far less likely to be prone to fatigue cracking of
the metal, which can occur in white golds, leading to prongs
which look good, yet are slightly cracked at prong tips, even if
only microscopically. These prongs are then prone to fail later
on, with potential loss of the stone. This problem is particulary
acute with fragile stones, or those with deep pavilions, or
anything else that can give a setter trouble, since he/she will
have to be far more careful fitting and shaping and bending the
prongs. That often means more working, bending back and forth,
and in general, messing around with the metal, to get it safely
set. (not like many diamonds where you can simply cut a seat,
place the stone, and push the prongs down once.)
Also, and perhaps most importantly, platinum has what is
described as a “dead” feel to it when bending. It does not
spring back at all. You push a prong down just snug to the stone
in white gold, and when you let go, it springs back just a little
and the stone is still loose. That means that you have to push
past the stone a little, to spring the prong into place. Or
you’re bending side to side, like closing a jump ring. Or who
knows whatall, to get the darn prong down tight. That nasty
spring back, coupled with the actual force needed to bend some
white gold, has broken a lot of stones, and Kunzite’s perfect
cleavage will give many a seasoned setter a bit of a worry.
Beginners, if they’ve done enough to know better, should pass it
to someone with more experience.
In platinum, though, the stone has a better chance of survival.
Platinum is not actually harder. but it has great tensile
strength, so settings once tight will stay tight, if they’ve been
made correctly. Part of this usually means avoiding long thin
prongs that have no undergallery to help support the prongs. You
CAN bend an unsupported platinum prong away from a stone more
easily if it isn’t heavy enough and you catch it right. Since
platinum prongs don’t so quickly wear down to sharp little edges,
and since you can set the prong tips really tight to the stone,
though, that catching is less of a danger. And with well made
prongs, when you go to set the stone, you can seat it precisely
and carfully, it doesn’t abrade the stone since at contact points
it’s not as absolutely hard and abrasive to the stone, and when
you bend the prong, it goes exactly to where you bend it and
doesn’t spring back. Overall, that is a lot less wear and tear
on a setters patience and strength, as well as a lot less risky
for the stone.
Same thing with bezels. if you need to burnish a bezel down, in
Platinum it takes far, far less effort and pressure to push the
metal to the stone, it burnishes down to a clean edge with much
less work and a better looking result, yet once done, is far
longer lasting and abrasion resistant (in terms of wearing thin,
not in terms of avoiding scratches) than white golds.
You can ask any setter whether they’d rather set fragile stones
in white golds or in platinum. The answer will be resounding
unanimity for platinum, at least amongs those not into masochism.
About it’s only weakness as a setting metal is that in bead and
bright cut type of setting, with normal steel gravers, the metal
does not bright cut, but comes out dull. You need to make up
carbide tipped gravers to get a good bright cut on platinum. And
THAT is a pain in the you-know-where. Carbide gravers are more
work to sharpen, you have to pretty much make them yourself from
square or round bar stock, and they cost more. But this is a
minor concern. For all other aspects, platinum is the metal of
choice.
Then simply look at platinum and white gold jewelry that’s been
in use for a while. Which one wears out faster? which seems to
loosen or loose stones more easily? Again, platinum is by far
the safer choice for the stones.
As with anything, there are no absolutes. You CAN break a stone
while setting it in platinum. And stones DO loosen, or prongs
can break. And the setting must be correctly designed with the
properties of both the stone and the metal in mind. Some designs
used for gold settings are less appropriate for platinum (and
vice versa). but all in all, it’s a far better choice if your
economics and skills allow it.
Peter Rowe
Hello Shari,
Kunzite is a variety of spodumene. Its color is pink to violet.
Some newly mined stones are often almost blue and will slowly
change to a rose-pink when exposed to the sunlight.
Under long wave UV light, kunzite will exhibit an orange glow,
less stronger under short wave. Under x-ray, kunzite will show a
strong orange fluorescence.
Right after being exposed to those conditions the stone will
phosphoresce, then, when the phosphorescence dies the stone will
appear green. But if the stone is exposed again to strong
sunlight for a few hours or heated about 200 C it will revert to
its pink to violet color.
Best regards,
Francoise.
Does that mean that the color of an old, faded stone can be
restablished witha 'shot of 200 C" . . . how bout Moranite…
which appears to do the same??
thanks,
Jim
Dear Shari,
Platinum is softer and more ductile than golds; It will bend
with a curve more readily than, say, white gold will. The
prongs or bezel won’t “pinch” the stone at the bend. Platinum
also has less “spring-back” or memory when bent. This quality
has been described as “deadsetting” ;i.e. it lays where you put
it. The cost of platinum is not as outrageous as you might
think, You can usually convince your customer of the added
benefits of its longevity.
However, you might want to try a less brittle stone your first
time around in platinum. A little experience will go a long
way…
Best of Luck, Eben
One of the funny incident I would like to share with you which
could be of some to you all. The short version of
this incident is that in month of july we had the production of
over 200Kgms of very nice color kunzitewhich were sent to our
Inventory house for cleaning . Well we were in the mountains
while sending the productions back for cleaning etc…so here
what workers did …they cleaned and washed the 200 Kgm of
Kunzite and after washing the kunzite , they put it under sun to
dry. After few days when we returned from the mining sites and
visited the inventory house…oh well …all the Kunzite had
fadded with the exception of few grams which were I guess away
from the sunlight . We have also posted some pictures on the
internet at http://www.gbaltd.com , under gba travels of our
mining sites in Pakistan Afghanistan. Best Wishes, Qazi