Opal Identification for Dummies

[WhingingPom]

Hello good people.

I've a ring that I bought which has a very pretty stone in it, but can't confirm in my own mind that it is what I think it is, a black opal.

I thought where better to get advice than the home of the Black Opal, 'Straya

I've done a fair amount of research and got some good information from watching videos of the good people at Black Opal Direct, and I've learned a few new words like potch, but I'm still not entirely sure.

I've included a few pictures of the stone, and there are other characteristics of it that the pictures may not pick up:

The flat part at the back of the stone is a pale grey (you could say dove grey) colour and in texture and resembles ice on a shallow puddle that some one has scattered grit over. Smooth here, frosty-looking there, and in places a build up of a sandy looking substance. Or sand.

I shined a torch light from my mobile phone directly on to this dove grey patch (or is it potch?) and there was no light that passed through to the face of the stone

When looked at under a loupe, the domed part of the stone has a few scratches and a very fine pit or two.

The ring itself is probably antique, maybe somewhere around the art deco period

It's probably impossible to tell from a picture, but if any one has any thoughts please let me know

Yours respectfully,

WhingingPom

P.S. Congrats on the Ashes (Whinge Whinge Whinge)

 

[Heatho]

Hi WP, we have a few opal experts around here, one I know personally and there is not much he doesn't know about opal.

Hopefully you will get an opinion later today sometime.

My opinion is that it's a quality opal and could be worth quite a bit of money depending on whether or not it's a doublet or solid crystal.

A photo of the back of the stone would be good as well.

Cheers :Y:

 

[WhingingPom]

Thanks for replying Heatho, that's very kind of you, I have a pic of the back but forgot to add it earlier so let's see if I can add one in this reply...

Hi WP, we have a few opal experts around here, one I know personally and there is not much he doesn't know about opal.

Hopefully you will get an opinion later today sometime.

My opinion is that it's a quality opal and could be worth quite a bit of money depending on whether or not it's a doublet or solid crystal.

A photo of the back of the stone would be good as well.

Cheers :Y:

 

[Heatho]

No worries at all mate, hopefully you can get an answer today, I'll send Syndyne (Shauno) a message and ask him if he would mind having a quick look for you.

 

[Wishfull]

You need to have light shining through the ring not on black plastic I recon.
Just my 2 cents worth.

 

[WhingingPom]

Thanks Wishfull, you;re right it would be best to pass a light through the main part of the stone.

The back is more of a grey textured affair, I'm holding out the hope that it may be potch, which may mean a solid opal

Though my thinking may be Wishful Wishfull

You need to have light shining through the ring not on black plastic I recon.
Just my 2 cents worth.

 

[grubstake]

The metalwork looks rather roughly finished (unusual for gold jewellery), but is the ring hallmarked or stamped with a carat rating? If so, it's gold and therefore the stone is probably an opal (although I doubt that it's a solid stone, from the uniform appearance of the backing). If not, it's most likely just costume jewellery - I believe faux opal used to be made from the iridescent wings of tropical butterflies!

 

[WhingingPom]

The ring is crudely stamped 18k (though I've acid tested it and am happy it is what it says it is).

Here's hoping no butterflies were harmed in the making of this ring! :8

The metalwork looks rather roughly finished (unusual for gold jewellery), but is the ring hallmarked or stamped with a carat rating? If so, it's gold and therefore the stone is probably an opal (although I doubt that it's a solid stone, from the uniform appearance of the backing). If not, it's most likely just costume jewellery - I believe faux opal used to be made from the iridescent wings of tropical butterflies!

 

[Syndyne]

G'day WP,

The ring is definitely of an older style (putting an exact date on it would be tough though). But I can say with 100% accuracy that the Opal is just a cheap triplet. It's basically made up of three layers -hence the name. It's compromised of a general base of potch, ironstone, glass or any darker material that will "kick" and intensify the lighter thin layer of Crystal Opal (yes, that is definitely real Opal) glued onto that. Then a Quartz Crystal cap is glued onto the the thin Opal layer.

If the stone was a solid Black Opal from here at the Ridge with that colour and pattern quality, you'd be looking at several thousand dollars per carat for the stone alone.

For a triplet like that, you'd generally be looking around the $25-30 AUD. The gold ring is your value there :Y:

Hope that helps and is the info you were after.

All the best,
Shauno

 

[user 4386]

Hi Shauno - the potch base is obvious, but how can you tell it is a triplet and not a doublet from the photo (especially given the scratches and pits that he mentions)? Seems strange to put such a triplet in a heavy 18 carat gold ring...

 

[Syndyne]

Hi Shauno - the potch base is obvious, but how can you tell it is a triplet and not a doublet from the photo (especially given the scratches and pits that he mentions)? Seems strange to put such a triplet in a heavy 18 carat gold ring...

G'day Goldierocks,

I can definitely see why you thought the ring seemed out of place for a cheaper stone. Although it looks to me to be a fairly small, light womens ring design of an older style.

I can certainly explain my reasoning for you.

What usually happens is a gem quality solid black opal is set in a good gold ring (assuming it was made here at Lightning Ridge originally and not from Coober Pedy or Whitecliffs), then something may happen to the stone over time ie; it's cracked or chipped from a knock, or age, or simply falls out and is lost. The quickest and often cheapest solution (rather than replacing again with a more expensive solid black opal) for most is to simply get a doublet (made up of a gem quality piece of solid crystal glued onto a black potch backing or other darker material), or as in this case, a triplet to replace the original stone. I see this quite often as my father is a part-time jeweller and has done this more times for people over the years than I can recall.

For me, the biggest and most obvious tell straight away is simply the Quartz cap. A good solid opal just doesn't look like that from any angle as the colour and dome of the cabochon would be displaying the pattern's colour play clear and bright overall across the entire surface. The picture with the ring on edge is a dead giveaway as you can see the opaqueness and pitting of the Quartz sitting on top of the colour. The picture that shows the colour much darker is also a dead giveaway as you can see the relatively flat opal surface set beneath the cap.

While triplets are an easy tell (as above) a doublet can be very tricky to pick when set as they are solid opal on top and usually proper black potch underneath. The only other way to really tell if it's a doublet is to see the stone's setting edge. As most of these are set into a ring bezel then this is hard to do without removing the stone and risking damage. A doublet will have a dead straight line between colour and potch with a possible black glue (normally blackened Araldite) line under magnification. Another way we tell is seeing the reflectivity of the glue surface through the crystal opal using a simple laser pointer.

As far as the surface pitting goes, opal normally won't pit like that. Definitely not at the frequency seen on the Quartz here anyhow. You might get one or two minute pits on a solid black or crystal opal that are only visible under extreme magnification. Though not very common, these can result from a contaminated cutting/polishing wheel as an example, or from tiny sand/matrix particles that were removed during the cutting process. You're more likely to see minute longer scratches across the surface of opal commonly due to the way we cut and polish the stones.

The discolouring between the Quartz, potch and thin opal layer will get worse and possibly more smoky yellow/white as the glue deteriorates. The very thin opal layer will most likely crack over time as well. We see that happen frequently in triplets due to having seperate substances of distinct hardnesses moving and expanding at different rates. However, if it's set very well and looked after, this may take many years or even lifetimes to happen.

It is always tough for those that have little to no experience or knowledge of opal to pick up on these things and can be heartbreaking for some when they've been caught out by spending an inordinate amount of money on a stone or piece of jewellery that is normally sold quite cheap.

Hope that clears it up and sheds a little more light on the subject. :Y:
Kindest regards,
Shauno.