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Agate-like banding in Ethiopian opal--paper #2!
https://www.gemologyonline.com/Forum/phpBB2/viewtopic.php?f=13&t=24467
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Author:  Stephen Challener [ Tue May 15, 2018 8:58 pm ]
Post subject:  Agate-like banding in Ethiopian opal--paper #2!

https://www.gia.edu/gems-gemology/sprin ... ke-banding
I'm really excited about this one! It's an article about the second-weirdest opal I've ever seen, written with Nathan Renfro (who needs no introduction). The photos turned out great, and the article even has some structural geology!

Author:  JCD [ Tue May 15, 2018 9:10 pm ]
Post subject:  Re: Agate-like banding in Ethiopian opal--paper #2!

Great article and pictures and a very interesting stone but now you have piqued my interest "second weirdest opal" ?

Thanks, Jim

Author:  Barbra Voltaire, FGG [ Wed May 16, 2018 12:25 am ]
Post subject:  Re: Agate-like banding in Ethiopian opal--paper #2!

Bravo, Stephen and Nathan.
Where the hell did you find it Stephen?

Author:  Stephen Challener [ Wed May 16, 2018 6:33 pm ]
Post subject:  Re: Agate-like banding in Ethiopian opal--paper #2!

JCD wrote:
Great article and pictures and a very interesting stone but now you have piqued my interest "second weirdest opal" ?

Thanks, Jim

Thanks for taking the bait. Once when I was young we were vacationing out west, and we met a guy who showed us an opal he'd collected himself in Nevada. It was, I kid you not, a perfectly preserved gooseberry. It had play of color. It had stripes. It had seeds. It was absolutely insane. In my opinion it is easily the greatest and most unique gem I've ever seen, including the entire Smithsonian display.

Barbra Voltaire wrote:
Bravo, Stephen and Nathan.
Where the hell did you find it Stephen?

I had seen a picture of a stone showing a similar pattern on facebook, and then at the very next gem show our local opal supplier had gotten in a really nice parcel of top-tier Shewa material. This stone was in that parcel. I found a very few more examples at Tucson this year, but they are very rare and most were marginal.

Author:  ROM [ Thu May 17, 2018 12:19 am ]
Post subject:  Re: Agate-like banding in Ethiopian opal--paper #2!

Quote:
Once when I was young we were vacationing out west, and we met a guy who showed us an opal he'd collected himself in Nevada. It was, I kid you not, a perfectly preserved gooseberry. It had play of color. It had stripes. It had seeds. It was absolutely insane. In my opinion it is easily the greatest and most unique gem I've ever seen, including the entire Smithsonian display.

That sounds amazing. Once, years ago, I spent a week mining opal with Keith Hodson at his Rainbow Ridge Opal Mine in Virgin Valley, NV. I was interviewing him for a profile I planned to write.

He lived in a small shack on his claim during mining season and he had amazing treasures inside. While opalized wood replacements and partial replacements called "conk" are fairly common at VV, he showed me his collection of black opal pine cone pseudomorphs -- cone-shaped openings left by deteriorated cones and later filled with the most amazing black precious opal. It shimmered with ultra bright play of color, mainly deep reds and greens. Unfortunately like much VV opal the casts had to be stored in water to prevent crazing. Still, it was the best black opal I've ever seen. They must be very rare and I've never seen anything like them since.

There's a hydrophane opal phenomenon that really puzzles me. Maybe I can find an explanation here. My first hydrophane experience came when I was wet-grinding what I thought was a piece of Mexican common opal: no play of color. But as it became saturated with water it burst into precious multicolors. But they were transient and disappeared when the opal dried.

Lately I've been cutting some Ethiopian Welo hydrophane and it behaves in exactly the opposite way: play of color when dry that disappears when wet, returning (much of the time) when it dries again. I've been calling it "reverse hydrophane" for want of a technical term. Some pieces are so "thirsty" it requires noticeable force to remove them from my wet fingers.

Does anyone have insight into those opposite reactions to water?

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