Great for show, please do not wear.
Given the particular length of the spine on your necklace (very cool) you could place your self in danger. Danger not from the venom, proteins etc......Danger from the actual trauma the serrations can/would inflict upon your neck.
The human neck is very, very,very vacscular as well as being quite supple. The average spine shed from even a juvenile ray could be 1 - 11/2 inches long.
The human neck in cross section is about 5 -7 inches.
The internal/external jugulars are merely 1/4 - 1/2 inch under your skin.
Do the math...........Awesome necklace........just be very careful if you actually wear it.