18k gold filled natural blue agate stone necklace Material: 18K gold filled Lobster clasp closure Length: 18' box chain Pendant measurements: 0.75'H 0.45'W gold filled is a beautiful more affordable alternative to solid gold as it is a genuine layer of gold permanently bonded onto base metal with heat and pressure that contains 100+ times more gold than gold plated. It is extremely durable, wont chip flake or tarnish