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 Post subject: Ethiopian Opal Agony and Ecstasy
PostPosted: Thu Sep 01, 2011 7:51 am 
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I got hooked on this material two weeks ago. There were obvious problems with its fragility. It's often difficult to correctly orient because you are unable to properly assess the life of the stone in its natural state. But it's soft and easy to work dry.

My first few stone cabs cut and prepolished to 600 grit dry then final polished with CEO2 wet. It's a nice finish but the opals usually lost their life and base color with the water. OK, I was told they would dry out. In Florida it's 60+% humidity all summer, and after 10 days it looked like no real change in the finished stones.

I got some DampRid, a desiccant, and put the finished opals in a container that was essentially 0% humidity. They seem to have dried out in hours, bringing back their earlier color and life. Two out of fourteen cracked and two others seem to have CEO2 discoloration. About 8 stones into my experience I started to completely wet the opal before CEO2 polishing and none of those have the discoloration. Looks like that won't happen again.

I wonder if wetting and drying the discolored stones might help them. I will look for some method of drying them that is less rapid but I don't have a way to measure humidity.

As usual, I know I've come to the right place. Thanks in advance for sharing your own past pain and perhaps sparing myself and others from the pitfalls.

Finally, these opals are freeeeeking awesome. I'm in love. I have three pieces of facet quality rough that I expect to produce some of the finest stones I've ever cut. That's next week.

Update: Looks like only one stone cracked and where it cracked was a clear weak spot so....not really a surprise. Also, the discolored stones have improved quite a lot over night. Go figure. Maybe they are absorbing water out of the air.


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 Post subject: Re: Ethiopian Opal Agony and Ecstasy
PostPosted: Thu Sep 01, 2011 9:14 am 
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Sounds like you have everything under control. But I'll mention that in my experience different stones show different levels of hydrophaneity. Some will saturate in seconds and completely dry out in hours (the drying process usually goes from totally clear->cloudy and crappy looking->back to appearance of the rough). Others will take hours to completely hydrate and can take literally months to totally dry out.

I cut mine wet so I don't have to worry about silicosis and I've never had a stone take up CeO. I have had a couple pull in some discoloration from using nasty old acetone to remove the dops, so I use clean acetone now.

Also, I don't know if you followed some of the earlier discussions on this material, but I and others recommend pavilion angles well below critical if you decide to facet your stones. I managed to kill the color play in a couple of really nice stones before I got my system down.

PS: I always like to see what other people are doing with this stuff. Love to see some pictures of your finished stones.

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 Post subject: Re: Ethiopian Opal Agony and Ecstasy
PostPosted: Thu Sep 01, 2011 10:34 am 
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bobsiv wrote:
Also, I don't know if you followed some of the earlier discussions on this material, but I and others recommend pavilion angles well below critical if you decide to facet your stones. I managed to kill the color play in a couple of really nice stones before I got my system down.


You're suggesting a faceted gem that has no working pavilion, like every native cut POS I've ever seen? 35 degree pav angles?

I defer to experience and will try that on the first one at least.

Worst opal photography ever:

Image


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 Post subject: Re: Ethiopian Opal Agony and Ecstasy
PostPosted: Thu Sep 01, 2011 2:46 pm 
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Enjoy the Ethiopian stuff! It can be a treat to work with and a bear at the same time.

Try adjusting your white balance on your camera, should help with the quality a bit:
Image


Bob is just suggesting you give the stone a deliberate window. We're not trying to highlight and reflect the body color of the stone when faceting opal with play of color except in special cases- doing so will drown out the play of color. It makes sense to cut to proper angles so the play of color magnifies and reflects, but AFAIK reality takes an opposite outcome. Plus with all those color flashing around the crown, no one's going to pay attention to a window. :)

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 Post subject: Re: Ethiopian Opal Agony and Ecstasy
PostPosted: Thu Sep 01, 2011 9:38 pm 
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ITD, there's a group of us who soak before doing anything. This actually helps show up internal problems and if it's going to crack, you want it to happen before, not during or after.
That said, you'll still more than likely get the odd one that will give up after finishing.
Also, some will revert fully back, some will stay clear, some can look quite yuck and some will never make up their mind, always changing with humidity.
They will absorb colours but if fully saturated before hand this should be kept to a minimum if there's any at all.

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 Post subject: Re: Ethiopian Opal Agony and Ecstasy
PostPosted: Thu Sep 01, 2011 9:56 pm 
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Your problem with CeO discoloration is not the CeO but rather the pigments used in the cheap CeO. Stick with either optical grade CeO or French Cerium, or try M-5 polish. Use them on felt for optimal results. I would also go much higher then 600grit before polishing. I go all the way to 3K pre-polish at minimum before the final polish. Sometimes even doing a 50K pre-polish. But the color bleeding issue is from cheap CeO and cheap diamond pastes using the pigments. I have never had any issues with the optical grade CeO from Vuclan Workshop, M-5, nor French Cerium.

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 Post subject: Re: Ethiopian Opal Agony and Ecstasy
PostPosted: Fri Sep 02, 2011 5:03 pm 
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Try an acetone soak on your stained ones. It may help remove any dye. It also dehydrates the material.

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 Post subject: Re: Ethiopian Opal Agony and Ecstasy
PostPosted: Fri Sep 02, 2011 7:05 pm 
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Looks like some nice bright material. Have fun with the faceting, the clearer stuff makes really neat cut stones (and if you're selling them, in my experience they go fast and at a good profit).

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 Post subject: Re: Ethiopian Opal Agony and Ecstasy
PostPosted: Fri Sep 02, 2011 7:36 pm 
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As usual, a wealth of ideas for the asking. Thanks all. This is without question the nicest, friendliest forum I've ever frequented.

I've switched over to a lot of Lambina opal for a couple days as the new ideas pour in. That never makes me uneasy.


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 Post subject: Re: Ethiopian Opal Agony and Ecstasy
PostPosted: Mon Sep 05, 2011 7:10 pm 
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I faceted three of these and posted photos here:
http://gemologyonline.com/Forum/phpBB2/viewtopic.php?f=8&t=3592&p=150280#p150280


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 Post subject: Re: Ethiopian Opal Agony and Ecstasy
PostPosted: Thu Sep 08, 2011 2:32 am 
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George, I know folks who have successfully get the CeO pigments almost all out with the acetone soak, but others had little to no luck. Same goes for diamond paste colors. So, seems like it depends on the type of pigment used.

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 Post subject: Re: Ethiopian Opal Agony and Ecstasy
PostPosted: Sun Sep 11, 2011 8:38 am 
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Has anyone tried to stabilize this material? I'm thinking maybe dunking one in half epoxy and half alcohol then see how it sets up. I have not the slightest difficulty rationalizing such a process.

Thoughts?


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 Post subject: Re: Ethiopian Opal Agony and Ecstasy
PostPosted: Sun Sep 11, 2011 11:20 pm 
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Jon, I have never had it happen personally to me. The ones I have seen it happen to have this real pinkish CeO, looks way to pink for me. I am thinking you may be on to something!!!! Maybe someone is using pigments to dye another cheaper compound the same color!

I have only had it happen with a cheap tube of diamond paste from China, lol.

To seal the opal simply take 1 quart jar of Acetone, squeeze in both tubes of Epoxy 330 clear, and dissolve. Now out your material into it. Soak it for about a week. Remove and let dry a few days. Remember to agitate the jar daily. This is the easiest method.

Best method is to use a coffee maker and heat your canning jar of Opticon. Tutorial is around here somewhere.

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 Post subject: Re: Ethiopian Opal Agony and Ecstasy
PostPosted: Mon Sep 12, 2011 7:11 am 
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This seems to me to be a method which could lead to that you sit with a bunch of close to transparent opals with a less than optimal color play. You have to check your opals before by soaking in water and see how they behave regarding to color play. Maybe I'm wrong about this. Have you found white/orange, opaque to translucent stones, to return to the original state after sealing, Swishman?

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 Post subject: Re: Ethiopian Opal Agony and Ecstasy
PostPosted: Mon Sep 12, 2011 7:29 am 
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Some look better when water wet, some look worse. Some change with the humidity, some don't. Some dry out back to original condition, some don't.

There's no rule as far as I can see. I'm sure some would look their best when epoxy impregnated.


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