Hi, my name is Eileen Procter and I am an metals conservator at
the Australian War Memorial. I have a piece of turquoise
jewelery set in sterling silver that has discoloured (yellowed).
The turquoise has not been in contact with the skin as the silver
forms a barrier. I have two theories about the discolouration:
that the heat from the wearers’ skin has heated something
(adhesive?) from the silver that has migrated through the stone
or 2. pollution from the atmosphere. I would like to know how
porous is the stone? and what would be the best way of cleaning
the turquiose? Thanks for your input. Eileen
This is totally conjecture, so I wish you would listen to the
other, more experienced jewelers, but ehre is my two cents:
Turquoise is porous. Actually, much turquoise that is mined is
chalk, and must be stabilized–mixed with a resin to harden it so
it is usable. Perhaps the resin itself yellowed. In which case,
there really probably isn’t anything you can do. Often turquoise
is color-shot, or dyed. Perhaps the dye was unstable. – Gary
Roman Owner, Fantasy Beads–Jewelry, Beads and Ethnographic Items
11254 Triangle Lane/Wheaton, MD 20902/301-933-8411
Hi Eileen, Gem Turquoise will not discolor, it is when you get
into soft turquoise that it will take on a different color. Like
a soft blue stone will turn green from a persons body acid. also
if your stone is from Australia and has been waxed when first
taken from a mine it is an off colored blue and it will turn a
funny colored brownish green, this is the actual color when
exposed to the air. The Austraian turquoise is a soft stone and
is usually treated with acrylics, The test for treated stone is
to touch it with cotton swab with some acitone on it. It will
change the color of the stone. Lloyd Have a very MERRY XMAS.
The porosity of turquoise varies inversely with the grade (the
higher the quality, the less porous.) Bottom of the line stuff is
refered to in the coloquial as “chalk,” as it is every bit as
soft and porous as chalk. All turqoise, however, is porous to
some degree, and sensitive to exposure to all sorts of chemicals,
particularly oils and detergents. My guess would be that the
previous owner of the ring wore it when they washed their hands,
or possibly when they washed dishes. I’m thinking the only way to
fix it is to repolish the stone.
Maybe some of the other subscribers have a more elegant
solution…
It may be that the turquoise was stabilized with some compound
that has yellowed with age, or possibly it was coated with a
substance that has yellowed.
It is not very unusual today to find stabilized turquoise…
usually an epoxy-like resin. It seems feasible that earlier
attempts at stabilization used substances that were UV unstable
and deteriorate with time.
If that is the case, even thought conservation is your mission,
replacement or recutting of the stone may be the only solution.
Hi, my name is Eileen Procter and I am an metals conservator at
the Australian War Memorial. I have a piece of turquoise jewelery
set in sterling silver that has discoloured (yellowed).
If the Turquoise has discolored yellow,it might very well be
that the resin used to stabilize it has aged,and turned this
color.Then it would be yellow all the way through the
stone.Nothing will help,except maybe a dying.It will dye
easily,all Turquoise is very porous. If it’s changed to green,it
is because Turquoise is a metallic,in the copper family,and it
has oxidized. This is on the surface only and you just
repolish.It’s easy.You use bobbing compound or the like,and then
white rough,or better Zam on a muslin buff.You could even do it
by hand in just minutes. Turquoise can also discolor from other
household contaminants,same solution,only you will have to sand
deeper.Point of interest,I saw mentioned “Australian” To the best
of my knowledge this is really not a true Turquoise,just a trade
name.It is Varacite,another soft look alike stone.
Mark Liccini
LICCINI
Gemstone Rough Dealers since 1970 U.S.MAIL
E-Mail: mark@LICCINI.com 107 C.Columbus Dr.#1A http://www.LICCINI.com Jersey City,N.J.07302
Voice Mail/Fax: 201-333-6332
This would be Gaspeite not Variscite, an (Fe++, Mg, Ni)CO3 Iron
Magnesium, Nickel Carbonate yellow green material, similar in
working properties to turquoise. Often called Australian
Turquoise.