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
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.