This is a lovely antique art nouveau baroque freshwater river pearl lavaliere pendant. 

The pearl is 6.00-7.00mm and very baroque and wrinkled. It is probably from the Mississippi river which was a large freshwater pearl producer at the time. 

It is made of solid yellow gold and features an art nouveau design. It is set with a single red stone that appears to be glass or paste. I measures 1 1/2 inch total. It is stamped "10K" on the bail.

All pearls are truly vintage and have only been lightly cleaned.