Old brooch or barrette maybe?

Not sure what it was. Been at the bottom of an old jewelry box for many years. You can see bits of green in the blue stone, through a mag glass. Can coral be blue? The little diamonds do have tiny inclusions and the pearls feel rough against teeth. Mounting looks cheap, no marks anywhere. Thinking I could maybe do something else withe the stones if it's worth doing. Necklace maybe? Any thoughts?

 

It looks like maybe molded blue glass. The top of the stone shows mottling, but the underside is solid blue. It's hard to say without seeing it first hand. The setting is plated, based on the loss showing on the back of the piece. I don't think diamonds would be mounted into a plated setting.
It's pretty, though!

 

Pretty, but costume... I can see the pearls coating (looking like a very short protruding tube) around some holes. As @stracci said, molded glass simulating carved stone, the "diamonds" are certainly rhinestones, 1920s era.

 

Agree with the others, pretty but costume. The blue glass looks Czech, they exported them too, and manufacturers in other countries would mount them in their own designs. The rough feel of the pearls could be wear to the coating, with tiny flakes coming off.

 

How long is it?
Looks like the back of a hair barrette.

 

Thank you for the quick ID. I have a lupe but never quite sure what to look for other than inclusions in some of these old small stones. You guys have been quite helpful in identifying the paste from the good stuff... I inherited several old jewelry boxes from my grandmothers, years ago and they were a mix of many different pieces, costume and fine alike. My wife and daughters took what they wanted right away but there was still some good stuff, as well as things like this, which are of questionable quality at best. In my opinion, even if it's from the 20's, paste is still paste and this piece will follow others like it into a box that will be sold as a lot on ebay at a later date.
I did find a couple of sets of Cartier cuff links as well as some Tiffany pieces, when I first received the boxes and have since sold them. Have a few more pieces that I'm not sure about, that I'll post at a later date. It's about 2.5 inches long. I also thought it might be a barrette. Thanks again.

 

Yep! The real pearls gritty feeling is unmistakable, something like a chalk rubbing on a blackboard

 

Just FYI - I've only found one barrette in the last decade that wasn't costume. That one was sterling and engraved with a friend's daughter's name. Said daughter got the barrette.

 

The only silver and gemstone ones I find are SW Native American.

 

Don’t be so quick to dismiss costume, there are some costume pieces that sell for more than gold and gem stone pieces do!

 

I just watched a Schreiner rhinestone pin, a nice one, sail past the $300 mark. A silver piece the same size might not do nearly as well and most likely wouldn't.