Vintage 80's 90's Givenchy Gold Tone Medallion Long Necklace Original Chain

I got this in the 90's. Givenchy medallion necklace in excellent condition. Gold tone is in fantastic shape. I have no idea what the black stone is in the middle - could be onyx, or glass. Chain is original and has the Givenchy tag on the end. Including medallion, necklace measures 28 inches long and 3 inch extender for additional length.