Oval shaped black opal I do believe blue green semi rough

looks like someone at one time was polishing this baby up. I have very little knowledge about opals if indeed this is a real opal.

What makes an opal valuable does size have much to do with it?

2 3/8" X 1 5/8' X 1/2"

I came across this stone at a flea market in New York

very hard the photograph it shows its beauty at certain angles.

 

I am not an expert, but this does not look like an opal to me. It looks like black Labradorite, JMHO

 

Or even dichroic glass.

 

It's spectrolite

 

Holly is right: variety of labradorite with more color display
https://en.wikipedia.org/wiki/Spectrolite

 

Thanks Marie Forjan, owedbybear, Hollyblue, and Kyratango for the lesson in spectrolite am a bit disappointed that it not an opal but wiser for the mistake.Thanks everyone

 

or Labradorite as Marie Forjan mentioned

 

Hard to tell from a photo and there are stones which can look similar..... https://thecitrinecircle.com/blogs/identifying-crystals/labradorite-or-spectrolite

 

Nice link Hollyblue Thanks This piece might have coe from the adirondack mountains upstate, pure speculation being that I live not too far from there according to one of the link it has been discovered there.

 

From searching the internet I found spectrolite is a type of labradorite

 

seem like the Finland labradorite is most commonly referred to as spectrolite which has a broader range of color. I hope I got that right that was from a link a bit earlier in the day.

 

Thanks for the link Hollyblue