Beautiful.

Greenish-blue stone – could be:
Fluorite – comes in various colors, including green and blue, often used for protection and energy cleansing.
Aquamarine – light blue or greenish stone that symbolizes peace, courage, and clarity.
Possible symbolism:
Protection: fluorite and iolite are associated with protection from negative energies.
I wore it only twice. I bought it for a dress for the holidays and haven't worn it since.