ALEXIS KIRK Hinged Gold Tone Metal Collar Necklace with Semi Precious Stones has a fold over lock clasp in the back. It hinges on both sides of the piece for easy wear. The curves are part of the design, and it measures approximately 16 1/4 inches closed. The stones are sodalite, onyx, carnelian and tiger's eye. I am not sure what the green stone is, and do not have a gem tester,. It is 1 inch wide in the front, and very elegant.