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Identifying opal beads


#1

Hello, Everyone! Sometime ago I took a chance on 3 strands of beads
labeled “opal”. I thought them to be too unexpensive to be the real
thing, but they are beautiful and so I added them to my collection.
It would be nice to know if they are real or a very good quality
opalized glass. They are mostly off-white with a blue/gray tint and
have a beautiful orange irridescency (hope this is the right word)
and will project an orange spot on a surface when you shine a bright
light on them. Upon inspection with a loupe I found some had tiny
bubbles in them. They do not seem to change much when immersed in
water, but one of the beads went from translucent to transparent.
The beads are not perfectly uniform, some are nor exactly spheric,
but about 12mm in diameter. In doing research on this I found pictures
of Dendrite (similar in color) and Jelly opal. What is the best way to
tell without taking it to a lab? And if they are a mineral and not
glass does anyone have an idea of the value? I want to use these as
accents on some pieces I am working on and need to know what to tell
my customers. Any help is greatly appreciated. Thank you very much! Vera


#2

Vera, Most Opals have a Specific Gravity (S.G.) of 1.9 to 2.5, whereas
most common glasses have a S.G of 2.5 to 2.9. So if you have a set of
S.G. liquids or know someone who does, you can drop one of your beads
in a liquid with a S.G of 2.5, if it floats it is most likely Opal. If
it sinks it is most likely Glass. If you can afford to sacrifice one of
your beads for science, put it in your kiln at about 500�F and cook it
for a while. If it is Opal, you will drive off the water of hydration
and the stone will probably crumble. Glass should be largely
unaffected. Regards …Bob Williams