Cleaning burnt emerald?

Is there any way to clean a burnt emerald? I was sizing a ring with
an emerald, I put chil gel on the stones, but some still were
affected by the heat. Any suggestions?

flexshaft and 3M radial bristle pumice disc the damaged part
off,prepolish with 3M radial bristle disc 80 grit keeping the facets
true as is possible, then cerium oxide or tin oxide for the mid
polish and finish with diamond paste polish on a clean cotton or
wool buffing wheel for the flexshaft…otherwise have it recut…I have
cut emeralds I find in my yard with dremel’s and a good index wheel
in a pinch-it’s super soft material and easy to create unique cuts
and faceted shapes or cabs…a final wax sometimes is called for to
bring out a particularly deep colour in the stone…depends on the
material you start with as to the possibilities, and/or the customer
whose emerald you cooked!

Hi Katherine,

You’ll have to be a little more specific about what happened. Did
the stones go black. Were they untreated or somehow filled. What
have you tried. We just need more info before we can answer the

Derek Levin

Hi Katherine,

Virtually all emeralds are “treated” - i.e. fracture filled in some
way. It could be with a natural oil, could be Canada balsam, could be
an epoxy resin. I’d guess you heated the stone enough to carbonize
that filling. If that is the case, you now have organic gunk baked
black in the pores and fissures of the stone, comparable to the
baked buildup in the domestic oven and similarly difficult to remove.
Fortunately the stone itself is pretty much immune to reagents. If
my diagnosis is correct I would first of all coat the stone with
"Easy-Off" or similar oven cleaner overnight. See what that does. If
this does not help (always assuming my diagnosis of burnt organic
fracture filling is in fact the correct one) you may have to proceed
to sterner stuff like boiling the stone in concentrated nitric acid.
If it gets to that stage and if the stone is valuable enough to
justify such a “rescue” I’d have this done by an expert. Hot nitric
acid - and similar aggressive reagents - should not messed with.
Once the residue has been dissolved out the stone will need to be
re-treated, again, a specialized process. Above all do not put the
stone in the ultrasonic. Most emeralds are flawed and fissured,
hence the prevalence of fracture filling. Ultrasonic may cause cracks
that went partway through the stone to go the rest of the distance,
leaving you with two stones instead of one, or worse. Been there
done that.

Hans Durstling
Moncton, Canada