Vintage Faceted Glass Teardrop Sterling Silver Pendant on Silver Tone 18" Chain

Vintage Faceted Glass Teardrop Sterling Silver Pendant on Silver Tone 18" Chain W/ Spring Ring Clasp. I call this the guitar pic necklace. This pendant has some weight to it and is suspended on a nice silver tone 18" chain. The pendant is marked sterling (ATI) but there are not markings on the chain, but it appears to be sterling but I won't say for certain. There is one tiny little pit in the glass as seen in the 3rd photo. Pre-owned, this necklace is in excellent vintage condition. The pendant tests high on the glass mark but also on the garnet mark on my Presidium gem tester. I don't know for sure whether it is glass or stone. N347