Hello I am cutting Labradorithe. My rough is not very good quality
from Madagascar. After I cut a stone I solve the dopping wax with
Methylated spirit. now after about a month the first stone I cut shows
a black line. There was a fine crack before but it seems that after
some time the crack turns black. Am I just mad and did not see the
line earlier or is there some kind of oxidation going on?
What can I do to prevent other stones from the same fate?
Wax? Glue? what does a professional lapidary do? Can I clean the crack
that is black already?
I am grateful for any help!
thank you!
greetings; i would recommend that doping any heat sensitive
stone----that you use a dab of super glue gel on the head of a large
nail. when you wish to remove stone, just apply a little heat to the
nail with your torch, and peel the stone off, immediately remove soft
adhesive from stone with a knife. take care---- dave.(18k)
First I would try my best to not cut a stone with a crack in it. I
have a cabbed many labradorites for customers that I have used
Opticon Fracture sealer to seal the cracks. Results were variable
because sometimes the sealer could not penetrate enough to make the
fracture less visible. Some of my lapidary friends who are still
cabbing use the automobile window glass sealers and are have some
great results. These sealers are highly viscous and set when exposed
to ultraviolet light. I do not know why the crack changed color.
Either you have gotten the crack contaminated of there is some kind
of oxidation occurring. Next time buy better material. I have paid as
high as $100 USD a pound for gem grade labradorite. Some of this
still has cracks, but the colors are fantastic and the cracks can be
orientated around.
Gerry Galarneau
Hi, Labradorite is very prone to fracture along cleavage planes. This
can make cutting quite frustrating. Depending upon the raw material,
three out of five stones may develop cracks and become junk. But the
stone doesn’t oxidize or turn colours or do anything fancy like that.
Chances are what made the crack go black is simply oxidation, over
time, of dirt/contamination in any of a multitude of forms, most
likely liquid: a drop of something absorbed from the workbench, oil
from the skin, dishwater, who-knows-what.
To “fix” such a stone is next to impossible and likely not worth the
effort. You might try soaking it in acetone, and if that doesn’t
work, other solvents. Then use opticon crack filler under a vacuum.
I’d say your best bet, though, is to simply soak the stone in hot
paraffin wax for an hour or two.
Cheers,
Hans Durstling
Moncton, Canada
I haven’t seen that happen but I suppose it is possible that the
meths is carrying solution into the crack which changes colour later.
Have you tried popping your dopped stones in the freezer for 30
minutes then ‘pinging’ the stones off with thumb pressure. Works every
time for me and I haven’t damaged a stone in the freezer yet (wouldn’t
put opal in there though!). For double cabbed stones (polished both
sides) I usually superglue (crazy glue, cyanocryllate sp?) a metal dop
on and knock off immediately polishing is finished. This seems to
leave fewer marks on the polished surface than dop wax.
Andy Parker, Agate House Lapidary
Ulverston, Cumbria, England
@Andy_Parker
Tel: 01229 584023