Joined: Tue Apr 06, 2010 12:00 pm Posts: 461 Location: Washington DC
Yeah, I was looking at the host rock in the back which is why I said it MAY be too shallow for faceting. Hard to tell.
I agree with Scarodactyl on your opal, looks like a nice piece to me. I have seen some truly bizarre Ethiopian opals, you can get all types of odd looking color play that are hard to believe are natural.
I know the crack is something that will affect the cutting of the stone, but will it affect the stability? Are all cracks signs of the whole stone's instability?
Here's a video of the opal:
Edit: Here's a few more images by me. I suck at taking these compared to the seller.
Joined: Tue Apr 06, 2010 12:00 pm Posts: 461 Location: Washington DC
Tough question, but in general opal is different from other materials in that you really don't want to leave any inclusions in the final stone. Especially with hydrophane opals any cracks are likely to grow and cause one stone to become two at some point.
What I do is soak the opal in a glass of water for a day or so, then leave it out to dry for another day, then pull the stone apart along any fractures. After that wahtever chunks I have are very likely to survive cutting in one piece.
Also, sometimes there are internal structures that look like cracks but are just density gradients or healed fractures. If you soak it and it doesn't split, it might not really be an inclusion/crack.
I would think that a crack like that one (single, straight crack, through and through) wouldn't be as indicative of instability as curved cracks on the surface would be, but that is based on intuition rather than data. What bobsiv said sounds like a pretty reasonable test, anyway.
I would think that a crack like that one (single, straight crack, through and through) wouldn't be as indicative of instability as curved cracks on the surface would be, but that is based on intuition rather than data. What bobsiv said sounds like a pretty reasonable test, anyway.
Sent it off to the Lapidary,
I'll let him know that I haven't performed any stability tests on it and let him use his best judgment on it. He did mention that it coukd be the same things you two mentioned, a previous crack that healed by being filling in, a density variation, or a darker material filled just happens to be there.
I've attached an image the Lapidary gave me. He's cut off the outer shell and the dark mark I saw was definitely a crack. He sent the image I've included below. He's cutting it into two stones, the matrix goes into the back quite a ways, so it'll lose some of its weight. After removing the mud shell the remaining rough weighs 6 grams, or 30 carats.
For a heavily frosted surface and non-optimal lighting/non-focused picture, the fire is actually showing pretty darned well IMO. Too bad it's lost weight, but I'm excited to see the final product(s).
Joined: Sun Oct 16, 2005 12:42 pm Posts: 2846 Location: Ho Chi Minh City, Vietnam
Have him send you a photo on a white background. What you're seeing with a black background is what they would look like as a black-based doublet. I've got one like that, looks fabulous against black, looks like nothing against white.
Have him send you a photo on a white background. What you're seeing with a black background is what they would look like as a black-based doublet. I've got one like that, looks fabulous against black, looks like nothing against white.
I suggested it, but he replied that he will just send them to me as he doesn't make a whole lot off of smaller projects.
A trick you can use is to put a bit of black epoxy on the backs. If you don't have black epoxy, you can mix a bit of black powder pigment from an art shop into regular epoxy and it works a trick.
I've done this mounting some light/translucent opals and it's enhanced their flash considerably. Of course you should disclose this if you're selling them.
Hope this helps
-Allan
_________________ Allan Aoyama http://www.omnifaceter.net <- Omnifaceter is back online!
Generally I would worry about putting a backing on them since it isn't a typical thing done to ethiopian stones. It might be accepted with Australian stones (and others like Spencer, Idaho) but I have a feeling that people would tend to look askance at wello opals with backings.
Above is photos of an opal I bought in April. 248.3ct.
I waited until now to send it out due to various reasons, but in other news: it yielded pretty well, Monday or Tuesday of next week I should receive a 113ct opal and a 25 ct opal from the Lapidary.
I'll post back with more images then. Is 55% yield decent?
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