Back to Ganoksin | FAQ | Contact

Diamond Cut Gems Only


#1

I have come across the caution “use diamond cut gems only”.
What are diamond cut gems? Is it a particular faceting? Why
would this warning be given? (some settings use this warning,
particularly with accent stones)

Also, what is “crazing” used in the description of an opal?

Thanks,
Bob B


#2

Bob, “Diamond cut gems” refers to stones that are cut with
pavillions in a more or less diamond shape .Sides pretty straight
from girdle to culet, as opposed to rounded bottom stones as cut
by 3rd world cutters looking to max out weight. Dia. cuts are
easier to set using modern “burr” methods. Deep belly stones are
VERY difficult to set in channels for example,( but not
impossible) Opal crazing is characterized by (usualy) small
cracks in a sort of spider-web pattern. Very non-directional, as
opposed to directional cracks caused by a blow or point pressure.
Cause of crazing is debated. Some is caused by water loss due to
evaporation from the surface of the stone.(Virgin Valley Nevada
material as example, although some is stable) Sometimes a opal
pocket (or field) will produce unstable material when,
historically, the mine or field has been good. A few years ago,I
bought a parcel of rough opal from Lightning Ridge and every
stone crazed,although it took 6 months for it all to go. Perhaps
our friends in Australia might be able to shed some light on
this? later- got to go see Richie Havens, MTR


#3

Diamond cut stones are stones that are cut similarly to or like
diamonds are cut, i.e. with no large bellies and fairly regular
faceting. It makes them much easier to set. Most “native” cut
stones are not diamond cut. there are many good sources for
diamond cut stones out there. Incidentally they are almost
always brighter and livelier stones than native cuts. Opal
crazing is lines in the opal that appear through drying and
ageing in some opals. It looks like fine cracks running
throughout the stone.Once an opal has crazed the value is
virtually nil,


#4

What are diamond cut gems?

Bob Diamond cut colored stones a re very well proportioned
faceted stones with out a bulged deep pavilion.

   Also, what is "crazing" used in the description of an opal?

Crazing in opal is the development of fine cracks radiating from
the surface of an opal due to internal stresses.

WayneM


#5

Diamond cut stones are cut to more perfect proportions than
native cut stones. Sometimes they are cut with more rounded
pavilions (the bottom of the stone). Hence they don’t fit into a
setting that is made for a diamond cut stone. Crazing is
something that opals will sometimes do when they dry out. I
have found that some opal will do this whether or not they are
kept in water or not. The really good stuff will not craze. Hope
this helps…Janine


#6

Dear Bob I am unfamiliar with the warning you speak of but "
crazing " in an opal refers to small cracks that can develop on
the face of the cab usually due to losing moisture in the stone,
a bath in glycerin once in a while will prevent that . Ron


#7
      I am unfamiliar with the warning you speak of but "
crazing " in an opal refers to small cracks that can develop on
the face of the cab usually due to losing  moisture in the
stone, a bath in glycerin once in a while will prevent that . 

I beg to differ, please.

While the opal won’t craze while it’ kept in plain water, since
drying won’t continue, this won’t heal anything that’s already
happened, and with the opals prone to craze, won’t replace any
lost hydrate content, nor will it slow it down again when the
opals are removed from the water. A good polish on the stone
will slow it down, but won’t prevent it, and coatings like oil,
or occasional soaks in anything, won’t prevent crazing when the
stones are then removed. Cutting the opal in the form of a
triplet, a thin slice sandwiched between upper clear and lower
(whatever) layers can protect that thin layer from crazing in
many cases, but with solid stones, that’s not an option. The
simple truth of opals is that some of them are going to craze,
and some will not, given normal care. The incidence varies a
great deal from of deposit/location to another. Mexican stones
are far more prone to it than are Australian stones. Idaho
opals too, are very frequently prone to craze. You simply need
to get them from someone who’s kept them around long enough that
the ones prone to crazing will have already started to do so, and
you don’t buy those…

Also, though I know that opal rough is sometimes packaged in
vials of glycerine, I recall being told by one gent who’s
knowledge of both opals and chemistry greatly exceeds my own,
that glycerine actually can draw moisture OUT of a material,
including opal. That would be the exact opposite effect from
what one would wish to occur. I’d suggest not using glycerine as
a bath for your opals. Plain water, if you wish something, is
going to be the best.

Hope this helps.

Peter Rowe


#8

Ron, If an opal is prone to craze,the only way to prvent it is
to submerge it in water (or glycerine, if you prefer) and leave
it there. These stones are not suitable as jewelry but can be
used as specimens.Once an opal starts to craze, there is no way
to un-craze it. Even re-cutting will only produce another stone
that will craze. Crazing is an inherent defect in the stone’s
structure. Moral: always buy opal from proven fields, from
dealers you trust who will guarantee it.
later,MTR