stone pendant

I've always called it a butterfly wing effect. Another term for it is schiller - but searching for that will lead you to more jewelry stores than jewelry terminology. Vintage butterfly wing jewelry, alas made from real butterflies, has the same look to it. The white version is often called "rainbow moonstone", a name that irritates the bejeebers out of me but it seems firmly established.

https://geology.com/gemstones/labradorite/