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Opal waste

Anyone, Question for any experienced opal cutters. I know Downing
and others say that your yield is often in the 20 - 40 % range per
stone, assuming you cut a viable stone out of the rough. What about
the yield of a parcel? I got a parcel of rough recently from Grawin
field - Lightning ridge. So far I got about 2 out of 5 stones to
face decently, and they’re pretty nice semi-black crystal, and
several carats each. The other 3 stones had alot of sand inclusions
under the surface that really badly weakened the stones to where
they came apart on the wheel despite the extra care on my part. Do
you always blame yourself or the material? I’m really a significant
novice, and got alot to learn, but anyone can take things slow and
turn down the wheel speed.

Bottom line - what yield do you get for the parcel, can you get 20%
yield from 40 -50 % (more or less) of the parcel stones? This would
give you about 10 % yield overall. Anyway, thanks for the input.


You have to start out by realizing that there are parcels, and there
are parcels. Then add that of course anything the miner found that
looked really good has already been removed. What you buy is what
they do not feel is worth their time/money to cut/have cut, but which
does still show some nice color. Usually you can see at least one
stone in there that should cut to give you what you paid for the
parcel, and the rest is “gravy”. So, the yield you should expect
will depend to a considerable extent on the cost of the parcel. And,
of course, how much you want to (or are able to) spend on cutting


  Bottom line - what yield do you get for the parcel, can you get
20% yield from 40 -50 % (more or less) of the parcel stones?  This
would give you about 10 % yield overall.  Anyway, thanks for the

Hello again Blaine It has been my experience that when buying a
parcel of opal, or any other gem rough, you should look for the one
or two stones that will “pay for the parcel”. In other words, a
parcel purchase will leave you with a lot of Junk and a few good
stones. This is quite a balancing act. I am of lately, beginning
to think that paying the “Pick Price” for the top stones is a better
business deal than buying a large parcel of stones. Here, you are
able to estimate return quite easily and not have the problem on
dumping the rest of the parcel when you are done. It takes some of
the risk away but not all. It also takes away some of the potential
rewards. Just remember, the safer the investment, the less chance
for high returns, and while a high risk investment MIGHT give great
returns, the fact that it is high risk indicates that it won’t.
Your challenge is to determine if it is a sure thing or a high risk.
Only experience will help you here, and that experience can
sometimes be costly. Just remember to look at the bad experience as
a learning experience. And only learn that lesson once.

On cutting returns, expect 20% to 30% return on a single piece of
rough. If you get above the 25% return, you are in the gravy. This
goes for both cabs and faceted stones. On a parcel, if you can get
20% return on the volume with 10 % of that being good quality, you
are doing good, if you bought correctly. Just remember that price
doesn’t necessarily equate to value.

By the way, those of you who are not familiar with Blain, he posted
a very unique opal some time back and then, the GIA, Gems and
Gemology, did a report on it. If you haven’t seen it, get a copy
and look at it. It is one of the most unique opals I have seen.
Unique and beautiful.

Don Rogers

Hi Blaine, There is no simple answer to your question. However…

When you purchase a mine-run parcel from an honest dealer, you
should expect to receive material which shows promise to the
discerning eye.

This -doesn’t- mean that every piece in the parcel will cut a
finished stone. It -does- mean that each chunk of rough in the
parcel is worth exploring. If you’ve found material for solid cabs,
with good color, in 2 out of 5 pieces of Lightning Ridge rough -
you’re doing just fine. (The stock answer is that a good parcel is
one which allows you to cut stones with a wholesale value of at least
three times the parcel price.)

Patience is the key to improving your yield. Don’t put a rough
stone anywhere near a power tool until you know what’s inside. Take
your time, and window each piece by hand on wet 320-grit Silicon
Carbide paper. Sooner or later you’ll find a stone that makes you
-very- glad you didn’t have a power wheel around when you hit color.

Finally…save the bright chips from the stones which fall apart.
They have value as inlay material.