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Author Topic: Estate sale jar of opal  (Read 394 times)

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irockhound

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Estate sale jar of opal
« on: June 10, 2017, 12:02:09 PM »

I know the jar was worth the $45. I paid but wondering how good it was.  I have cut a few opals but I am don't cut it often and I don't know why it scares me to screw up opal when I don't have a care in the world cutting agate.  I have put some arrows on the pics and wonder if these are normally considered black opal.  Some some great Bright blue flash with some black areas and grey opal surrounding.  I know that each stone is unique and depending on fractures and inclusions what looks good could be terrible.  Just wanted to share the pics and get a feel for what I got.  The plate is about 7" across.

I would love to find someone who could give me the finer points of orientation and Opal cutting.

Thanks, Steve
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rocks2dust

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Re: Estate sale jar of opal
« Reply #1 on: June 10, 2017, 12:18:53 PM »

Some pretty pieces in there - nice find. On my monitor, most of the opals in question look blue. That said, it is difficult to know from a photo what is body color and what may be color play. Some might even be described as "dark" blue. They really need to be cut for a final determination, based upon a face-up evaluation of the cab. There is a good explanation, along with a chart of body tones on this website.

Are they Nevada, or from somewhere else?

irockhound

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Re: Estate sale jar of opal
« Reply #2 on: June 10, 2017, 12:24:18 PM »

Great webpage that gives a good explanation of the colors and matrix.  Thanks for that link.  I zoomed in on one of the pictures before I reduced for posting to give a better indication of a couple of the opals.

As for location you never know what might get mixed in over time.  Definitely doesn't look to have any Mexican included although they did have another jar of those.  There might be some Spencer in here but I seem to remember the Spencer having a brighter white matrix.

The Mexican I have kept in the jar so far.  Last couple of jars I dumped out in a tray and let the water evaporate to see what lived or died since the problem of hydration and fracture on releasing the water content.  I figured I would hold on to the nicest jar and find out the best process for slowly letting the excess water out so reduce the number lost to the shock of quick water loss but I don't know that method yet.
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gemfeller

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Re: Estate sale jar of opal
« Reply #3 on: June 10, 2017, 12:55:06 PM »

The ones with arrows all appear to be black opal but I'm a little puzzled by the one you highlighted in your last image.  It's a very odd stone to my eye.

I've been cutting opal for a lot of years and can ID material from most regions.  If you'd like me to take a personal look since I'm nearby, give me a holler.  I agree with R2D that images can be a little misleading.

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ileney

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Re: Estate sale jar of opal
« Reply #4 on: June 10, 2017, 02:25:10 PM »

The dark blue one that is slabbed on one side sure looks like lightning ridge black Opal with blue fire to me. Is the blue geodish one a different stone or was that prior to cutting?
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irockhound

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Re: Estate sale jar of opal
« Reply #5 on: June 10, 2017, 02:26:07 PM »

Yes I agree and always happy to see you.  The last image of the Opal the rind looks more like a Rhyolite close up doesn't it.
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irockhound

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Re: Estate sale jar of opal
« Reply #6 on: June 10, 2017, 02:38:57 PM »

All of the stones are just as they came out of the water and I haven't worked any yet.  The estate was from a jeweler   and gem dealer.  Just crazy what they sold for pennies on the dollar at it, don't think I will ever see a sale like it again.  Foolishly I didn't drain the bank and buy it all.  Faceted large 2 carat and up to 13 ct Blue Topaz, Ametrine, Kunzite and Gold Beryl for about 3 to $4.00 each. I was just brainless not spending more ( I did buy a bunch of the faceted stones thank goodness).
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Neural

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Re: Estate sale jar of opal
« Reply #7 on: June 10, 2017, 06:13:33 PM »

Definitely a mix of Lightning Ridge and Coober Pedy.  that was a good find for just $45.  I think just one of those plates alone would be $45.  It looks like a few "nobbies" in there as well (I'd cut those last if you are in need of practice, as they can be rascals, but also very worth it).
Definitely read up on opal cutting if you need a refresher.  You've got what looks like 3 or 4 different types of rough to work with (not meaning location, but how the fire/potch are going to interact).
First, there appear to be some pieces that are opalized shell fossils, or pieces of that.  The give-away there is going to be a precious/semi-precious opal with rust red base material around it.  Fortunately, because the shell basically turns into opal over time, they tend to clean up nicely.  The down side is that the opal itself isn't always the best quality, and can be hard to cab due to the curved nature of the shells.
Second, there appears to be some basic white pinfire.  Again, rust red base material that can be ground off, but the quality of the opal can be low as well.  On top of that it's more random on where the base/inclusions are, so you might have a clear face, but cut in a little further and find some rust red rock right in the middle of your cab.   If the piece is thin enough to start with (as in 1/2" thin, you can use a bright light and "candle" it to look for areas that don't let as much light pass through.  It's no guarantee, but it gives you an idea if there may be base material/inclusions inside what you see on the surface.
Third, there's the Lightning Ridge material.  Not as easy to candle, and from what you have there, looks mostly like blue/green fire (lower in value than red/orange/yellow).   Black Opal rough, in my experience, tends to have a base material than is much less dense than the rust red stuff from Coober Pedy, and acts a lot like cavities in teeth in how it appears to have eaten away at the opal material.
Fourth, the nobbies are nodule like formations of opal that tend to try and hold their treasure in their center.  This does not mean to go and just cut them right in half however. :)

With the second and third types, it's important to remember that you can try and grind away an inclusion or bit of sand, but if you go too far, you may just cut through the entire color bar as well.   In a perfect world, opal would be like two layers of chocolate cake (the base), with a layer of frosting (the fire) between them so you could just take off the top layer and expose the fire.  Unfortunately, opal fire doesn't work that way, as color bars tend to be undulating sheets of color that curve and flow and vary in thickness etc.

Feel free to post close-up pics if you want opinions from people on which would be a likely stone to start with with little risk of loss if you make a mistake.

And finally...  I'm not an expert, and cannot guarantee that all my information is 100% accurate.  Just going by what I remember and have experienced myself. :)
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ileney

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Re: Estate sale jar of opal
« Reply #8 on: June 10, 2017, 08:33:25 PM »

What a fabulous find! I hope you post the faceted stones too for us to admire, as well as any opals you finish.
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irockhound

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Re: Estate sale jar of opal
« Reply #9 on: June 11, 2017, 12:30:46 AM »

@ Neural, thanks for taking the time to write such an in depth post.  All that info is appreciated greatly.  I will be taking my time with them and in no rush to make mistakes.  I wonder with the color bar changing directions and not having a flat bar to work to how you deal with them without carving them like a Fire Agate.  I have one piece than I can see the bar flat for 2/3 of the stone and then it dives at about a 30 degree slope, how do you normally deal with stones like that especially if the back is relatively flat so the color bar is moving towards the back of the piece?
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ileney

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Re: Estate sale jar of opal
« Reply #10 on: June 11, 2017, 05:22:41 AM »

I highly recommend Paul Downing's Opal Cutting Made Easy. He also wrote an advanced opal cutting and setting guide. He describes step by step instructions, with pictures and diagrams. Also, Black Opal Direct has a ton of opal cutting videos on YouTube.

Good luck!
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mirkaba

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Re: Estate sale jar of opal
« Reply #11 on: June 11, 2017, 08:25:07 AM »

Nice find. Looks like a good batch of Opal to start out with. I say jump in with both feet. Start with the least colorful and work up to the best. Work on exposing the color first and then work around and up to the flash. Good luck..............Bob
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ileney

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Re: Estate sale jar of opal
« Reply #12 on: June 11, 2017, 08:54:34 AM »

Just looked again. The advanced cutting guide is $29.95 new on amazon. It's called opal and gemstone jewelery, cutting, designing, setting,  a step by step cutting guide by Paul Downing. It also has good tips on proper setting of Australian Opal to avoid cracking or chipping and information on making doublets, which I am first experimenting with now.
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Neural

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Re: Estate sale jar of opal
« Reply #13 on: June 11, 2017, 09:30:33 AM »

I highly recommend Paul Downing's Opal Cutting Made Easy. He also wrote an advanced opal cutting and setting guide. He describes step by step instructions, with pictures and diagrams. Also, Black Opal Direct has a ton of opal cutting videos on YouTube.

Good luck!
Just about anything by Mr. Downing is worth reading.   Highly recommended.
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Neural

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Re: Estate sale jar of opal
« Reply #14 on: June 11, 2017, 09:35:32 AM »

  I have one piece than I can see the bar flat for 2/3 of the stone and then it dives at about a 30 degree slope, how do you normally deal with stones like that especially if the back is relatively flat so the color bar is moving towards the back of the piece?

A lot of that depends on the size of the stone.  If it's large enough that you can cut a cabochon out of the area where the bar is nice and flat, then you can get away with trimming off the sloped area.  The cut off, if thick enough, can then be cut such that the bar it contains is flat and create a smaller cab with it.   If the stone is only around a centimeter or two across, consider cutting the cab so the top is at the "peak" of the curve.  Work with the fire to allow the curve of the color bar cover as much of the face as possible.  Even if you end up with a relatively high dome stone, you have a potential with smaller stones like that to maximize the use of the color bar.  Have to think a little outside the box with that stuff. :)   If my explanation on the orientation doesn't make sense, let me know, I'll throw together a diagram. :)
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