Agree with Todd. Storing cut opals in distilled (or any other) water
is sheer nonsense, one more in the vast catalogue of opal myths. No
other stone it seems to me has collected such an aura of hokum and
buncombe of the “oh my gosh never do this, never do that” variety. In
a sense one can take these myths as a backhanded compliment to the
opal, as being, of all stones, the most magical and mysterious.
I have done experiments, just out of curiosity, with water and opal,
specifically Welo hydrophane, leaving two pieces in water for
One piece I recall absorbed 3% of its weight in water in the first
24 hours, and no more thereafter, the other 1.9 percent, similarly.
With Mexican opal, and for that matter any questionable - i. e.
primarily volcanic hosted - opal, a recommended practice is to is to
abuse it for six months or so, leave it outside on a hot tin roof or
somewhere where there’s lots of temperature change. If after that
time it hasn’t crazed it’s assumed to be safe to cut. But that’s a
rough and ready rule which does not by any means give 100% assurance.
In a baggie pinned to my corkboard I have before me as I type two
Mexican fire opals, one an emerald cut, the other a step cut, each
about 2 carats, both cracked through and through. The emerald cut I
had in my gem case for something like eight years, through all kinds
of temperature changes like being left in the car overnight in
Canadian winter on more than one occasion. Never bothered it. Then,
having put in its eight years all of a sudden it decided to crack.
Why? Who knows.
In a general sort of way opal rough is sold in water filled bottles
precisely for the reason Todd mentions: the water approximates what
the opal will look like polished. Also (more subtly) the curved glass
of the bottles acts as a magnifier - makes it look like you’re
That’s not deceptive, it’s just the way it’s done. That being said
the water does also conceal cracks. Again that’s a known fact, and
thus any serious buyer of opal rough will take the stone out of the
bottle and look at it dry before buying.
That’s rough opal. Cut opals are stored dry, the way they will be