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Stabilised Grade 2 Turquoise


#1

Hello from sunny Bognor Regis, UK

I’ve got these turquoise cabochon ‘stones’ described as ‘stabilised
grade 2’. They look like resin to me! Can anyone tell me what has
been done to the stone to stabilise it and what this means? What do I
need to know about setting them and polishing the finished item? I’ve
been reluctant to use them as I don’t want to waste valuable time and
materials only to ruin the ‘stone’ in the polishing.

Thanks for your help

Col
Collette Batho
www.collettebatho.com


#2
I've got these turquoise cabochon 'stones' described as
'stabilised grade 2'. They look like resin to me! Can anyone tell
me what has been done to the stone to stabilise it and what this
means? What do I need to know about setting them and polishing the
finished item? 

If you use Zam on a muslin buff it will polish both the stone and
Sterling silver even if the stones are treated. It also does a pretty
good job of polishing gold. You might run into trouble if you try to
polish prongs or bezels with small rotary wheels after the stones are
set which might gouge the soft turquoise, but most silicone wheels
should be safe. Test them on a small area of the stone’s back or
girdle to be sure and prepolish rough areas in the metal before
setting the stones.

There are several turquoise treatments. One old method involved
infusing epoxy-type material into porous “chalk” turquoise under
pressure. That increased hardness, stability and improved color
somewhat. Some epoxy processes also used dyes to enhance color. A
newer more sophisticated treatment called the Zachery process
requires gem lab methods to detect. Chances are your stones were
treated by one of the old methods.

As for “Grade 2,” that’s a supplier designation and not a widely
used trade term. It means what the supplier says it means, but it’s
definitely lower quality than “Grade 1,” LOL. If they look like resin
that’s probably what they are.

Rick Martin
www.artcutgems.com


#3

HI Col- I am not a big time expert in Turquoise but I think I can
answer your questions.

  1. “Grade 2” is pretty much meaningless. There is no common
    grading/rating scale for turquoise. Some vendors will make up a scale
    for their own use, but telling me a piece of turquoise is Grade
    AAAAAA or grade 2 just does not mean anything. Hardness, color,
    matrix and the indefinable “Zat” determine turquoise quality.

  2. “Look like resin” Could be. There are different classifications
    of turquoise. They aRe: Natural turquoise- cut, polished, may have
    backing but no other treatment to enhance color or hardness> This is
    the top grade only about 3-5% of turquoise is of this quality.
    Stabilized- Lower grade turquoise or chalk is treated to improve
    color and hardness. There are several stabilizing treatments but most
    require soaking the stones in some kind of epoxy solution or
    plasticizer for a week or so. Sometimes dye is added to enhance the
    color during this process. Other treatments to enhance color may be
    used. “Reconstituted” is low grade turquoise ground up, treated with
    color enhancing dyes, mixed with epoxy resin and pressed out into
    blocks or molds. Lab or synthetic turquoise is entirely man made and
    has never been in the ground. Several plastics are used. So your
    stone has at least been treated to make it harder and probably color
    enhanced. That is not necessarily bad as long as you know what you
    are getting. Natural stones are more likely (particularly in rings)
    to change color over a long period of time

  3. I always use bezel to set the stones, I usually add some padding
    before placing the stone. The padding can be sawdust, paper, cloth
    etc. I usually use felt and hammer it if it needs to be thinned. NO
    SOLDERING WITH THE STONE SET ( unless you take special precautions)
    as turquoise is quite heat sensitive and will just disappear or crack
    if you get your torch too close.

  4. I do my final polish (usually sterling) after the stone is set.
    Recently, I have been using Zam and it will polish the stone as well
    as the silver. If I had a “stone” that was damaged by a light buffing
    with Zam, it is too low grade to try to sell anyway. I use an
    ammonia/water mixture with a squirt of dishwashing liquid in an
    ultrasonic cleaner for cleaning.

  5. Lots of stuff ( plastic, dyed rocks) is sold as turquoise. I will
    not buy Chinese Turquoise because I have had so many cabs break
    during handling or setting. It is very difficult to know what you are
    really buying for stuff labeled turquoise and what kind of treatment
    it may have been given. One of my favorites was a recent item,
    obviously made of plastic or similar, being sold as turquoise. When
    the vendor was questioned, they said they meant that it was a real
    turquoise color rather than real turquoise.

  6. Good luck. If what you have does not work out, send me an email
    and I will send you a couple of good quality natural turquoise cabs
    to play with (free of course).

Jim J


#4

They are normally inpregnated with resin and dyed to make them an
even colour… The surface is usually very durable but the colour
depth and impregnation may be variable dependant upon the porosity
of the original stone.

Nick


#5

Hi all

Just want to say thank you to everyone who replied to my query about
using stabilised turquoise. I have used a couple of these stones now
with satisfactory results. I can’t show them on my website yet as
they were commissioned for gifts that won’t be received until the
end of April. You are all so generous in your advice.

Thank you
Collette
www.collettebatho.com