My first thought was agate, but upon closer inspection, this stone has some mica flake included which makes me think closer to aventurine. I'm moderately sure this stone has been color enhanced. The crystal is a genuine Swarovski 1088, size pp32.
This 18mm x 25mm cabochon has been wrapped with gold colored tarnish resistant wire in a complex interlocking design, featuring a basket weave, swirls, and a large integrated infinity bail.
Completed with a slick braided cord necklace, adjustable in length between ~25.5" and 27".