What could this stone be?

[Lilybean]

I recently acquired this stone. It was described to me as an 'oval cut cab stone 29mm x 19 x 10mm, translucent light brown with moderate violet small flask pattern'. I am not totally convinced it is nothing more than plastic to be honest, but thought I'd see what you all had to say. The pictures don't do it justice as the flecks look blue in the photos, but are actually bright purple. What concerns me is the back of it. It almost looks like some kind of coating. It is clear by the markings on the back that it was glued into/onto something, but then there's the chunk that looks rock-like. Any ideas?

 

[kenny]

Opal?

 

[Richard M.]

It's almost certainly an opal, probably Australian in origin. With opals it's not considered objectionable to leave some cavities like that on the reverse side as long as they don't interfere with the stone's outline symmetry, don't pose any structural problems and can't be seen when the stone is face-up. The stone appears in the image to be near the junction of light and dark opal in body tone.

Richard M. (Rick Martin)

 

[peacechick]

The translucency seems to suggest a black jelly opal maybe? If you google it, the ones that appear look quite like yours.

 

[Lilybean]

Is the coating on the reverse just that; a coating? I was also wondering if it could be an Opal. I've seen a lot of photos online and actually own a lot of opals (October/Libra baby), but all of my opals are light/white. It's a beautiful stone in person and VERY large! So when they said "cab stone" that's just referring to the cut; oval?

 

[Richard M.]

Is the coating on the reverse just that; a coating? I was also wondering if it could be an Opal. I've seen a lot of photos online and actually own a lot of opals (October/Libra baby), but all of my opals are light/white. It's a beautiful stone in person and VERY large! So when they said "cab stone" that's just referring to the cut; oval?

Trying to identify stones from on-line images is fraught with potential problems. First, I can't see what you're referring to as a coating on the reverse. I see what appear to be some scratches in the center of the lower image. Could you describe more clearly what you have in mind?

"Cab" is short for "cabochon." It's a French term for a type of cut. It literally means "like a bald head," referring to the smooth rounded crown. Cabochons can be cut in many shapes, not just ovals.

Opal body tone can range from white (N9) to black (N1). Body tone is divided into "light" opals (N9 through N7), "dark" opals (N6 and N5) and "black" opals (N4 through N1, N1 being jet black). All things being equal (which they seldom are) black opals are the most valuable, white opals the least. Many factors besides body tone affect opal value, especially the quality and brightness of the play of color (which the blue/purple flashes in your stone would be called.)

One of the prominent figures in the early days of the Gemological Institute of America said of grading gems, diamond is the simplest while opal is by far the most difficult.

Richard M. (Rick Martin)

 

[Lilybean]

Yes, I completely understand what you mean about online, etc.

In researching and actually seeing the stone in person, I think it is an "Opal Triplet" which is the "coating" I keep referring to. And the more research and all of your great descriptions and knowledge, I do believe it is an Opal. I will add it to my items to take to a jeweler for clarification.

Thank you all for your input! This is a great forum!

 

[Agneau]

Do you have a picture of it from the side view?

 

[hippi_pixi]

it could be a doublet? a triplet when viewed side on will have a layer of completely transparent material on top, a layer of opal and then a backing for strength.

a doublet is just a thin layer of opal stuck onto a backing for strength. from my understanding many opals are commonly cut to include a natural stone backing for strength so the opal will naturally have a layer of stone on the back which is perfectly normal. where a perfectly good opal is thin and therefore weak they stick a backing on which can be stone or something else. the only downside of this is the potential for the glue to deteriorate over time. and value as obviously 100% natural stones are worth more than ones that are tampered with.

a good shot of the side of the stone will tell more about wether it is solid, doublet or triplet