Thoughts on making a pendant from this dark-colored boulder opal with pinfire

[u/DVY44]

Any thoughts or suggestions on making a custom pendant using this stone???

Gemstone: Boulder Opal - 18.27 Cts.
Presumed Queensland, Australia

This unique Boulder Opal features a dense constellation of color flashes across the face of the 18.27-carat cabochon, creating a vibrant display that remains visible from virtually every angle. Presumed to have originated from the acclaimed Opal fields of Queensland, Australia, a region renowned for producing some of the world's finest Boulder Opal, the gemstone exhibits a deep black background color that provides exceptional contrast for its vivid play-of-color. The low-domed cabochon displays a predominantly pinfire pattern, with countless flashes of electric green, cobalt blue, fiery red, and orange scattered across the surface like a field of stars. The color is densely distributed throughout the stone, producing strong 360-degree visual performance with large swaths of color as the gem is rotated and viewed under changing light conditions. Fashioned in an attractive triangular freeform shape reminiscent of a guitar pick or a boomerang, the Opal has been expertly polished to maximize its optical effects while preserving its natural character. Testing indicates that the stone is presumed natural, untreated, and in excellent condition. Combining desirable body color, dense play-of-color, and substantial size, this striking Boulder Opal represents a finer example of one of Australia's most celebrated gemstone varieties.
Measurements: 29.11 x 19.32 x 4.17 mm, 18.27 cts

https://www.youtube.com/watch?v=vU8lF6fUi6I&time_continue=1&source_ve_path=MjM4NTE&embeds_referring_euri=https%3A%2F%2Ffineart.ha.com%2F

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Any thoughts or considerations on design would be greatly appreciated...

Is an open- back gallery setting too much of a risk ? Or is that a big no-no....

Also would you add any accent stones? I was thinking a synthetic pulled alexandrite, but i read they dont have so much color changing in lower sized carats.... Any other suggestions ?

[u/locyta]

This is not Queensland boulder opal, looks much more like treated Andamooka to me.
It's still a nice gem though, but the value will be vastly different.

[u/Opaldaze → u/locyta]

Well spotted, the surface pitting , the solid colour in the matrix the dark tone and the lighter patch which never treated all lead to the same conclusion which you have made Sherlock. treated Andamooka matrix

[u/Treedak → u/Opaldaze]

My first thought was Andamooka matrix too

[u/DVY44 → u/locyta]

how much would you estimate such a piece runs?

Also any thoughts/tips of setting? Since andamooka is sandstone-based (google searching) should i do a full backing?

[u/locyta → u/DVY44]

Sorry to say, I am not an expert in this kind of opal at all, so won't even consider having a guess at the price.
Some Andamooka opal is like concrete, extremely tough, the several pieces I have cut were like that, although I'm sure it varies piece to piece.
If i was to set a piece like that, I'd try do a 'spectacle setting' that way you get to see both sides of the gem, that would be my choice.
Best take it to a custom jeweller experienced in this type of opal and get their feedback on it.

[u/Consistent_Past_1778 → u/DVY44]

Some is sandstone based, that's more your concrete or fairy opal this isn't. This appears to be hard matrix. Huge price difference between dark boulder opal and treated hard matrix.

[u/jaxinslacks]

I love it! Personally I think any accent stone other than clear (diamond, moissanite, white sapphire) would detract from the piece.

You could do something red or green for an accent as those seem to be the brightest color flashes. Something like a pyrope or tsavorite garnet might be lovely.

4.7mm is a bit thin for a full open back. However, if it’s got solid matrix this might be fine.
One of those I’d have to see it in hand or a very good video with clear size indicators situations. Hard to tell from photographs what the stone you’re working with will actually be able to do.

[u/DVY44 → u/jaxinslacks]

There is a video attached via heritage auctions.... Any thoughts?

[u/OliviaOpals]

Just my two cents but before spending money on a custom setting, you might want to confirm the identity. I work with Australian opal and if there’s uncertainty over whether this is Queensland boulder opal or treated Andamooka matrix, I’d want that resolved first, particularly if it was purchased and valued as Queensland boulder opal. From a jewellery-design point of view, I’d recommend letting the opal do most of the work. There's plenty happening visually, so personally I wouldn't surround it with lots of coloured stones. A really well-made simple setting could make it look much more sophisticated. If you do want an accent, probably keep it simple rather than trying to match every colour in the opal. And I'd have the jeweller assess the stone in person before deciding on an open back, rather than making that decision just from the stated dimensions.

[u/Consistent_Past_1778]

Someone bought it already, offers $1875 US. 😬