Brad Simon, publisher of -Bench newsletter and Bench magazine is a
frequent contributor here. A series of articles authored by me called
"Colored Gemstones at the Bench" have been featured in both the
newsletter (abbreviated form) and the magazine. These articles
address some of the characteristics of common gemstones and how they
should be handled at the bench. Brad’s newsletter is free to all who
request it at http://www.bwsimon.com/e-bench/ and I receive no money
for my articles.
To more directly answer your question:
Tanzanite should NEVER be placed in an ultrasonic cleaner. It MIGHT
survive, but I have seen ten carat plus stones instantly and
completely destroyed. Tanzanite is soft, brittle and very sensitive
to thermal shock, I.e., sudden temperature change. Placing a stone
into hot pickle is a questionable practice, and extended stays in the
pickle can adversely affect the surface of a polished Tanzanite,
depending on the composition of the pickle.
In and of itself, emerald is very hard and quite durable.
Unfortunately. most of the emerald that comes across the bench has
been treated, and sometimes that treatment hides the many small
fractures that may be present. Those fractures are planes/areas of
weakness in the crystal, and sudden changes in temperature or a
little too much pressure from a setting tool, and, “POOF!”. This has
led many to think emerald is not hard or durable, but "clean"
emerald presents little problems in handling. But, you may never run
a cross one.
Peridot does not seem to suffer from thermal shock or the vibration
of an ultrasonic, but most pickling soultons will quite rapidly etch
the surface, calling for a complete re-polish or re-cut of the
stone. Repalcing a 1-2 carat peridot will not break the bank,
but…if you have not checked the prices of peridot in the four
caratand uprange lately, you may be in a for a real shocker. For
good Pakistani material over 5 carats, expect to pay at least $150/c
and for stones 7c plus, much more. After Tucson, we will all be
seeing the results of the weak dollar in colored gems and many US
jewelers will definitely have sticker shock. So keep the peridot
away from the pickle!
Soap and water with a soft toothbrush cleans everything!