Found this while on a hiking trail, very maluable, PD stamped on back, black spots on sides edges of cross are reflections of my phone, about 1.2 inches in length, no marking on inside of where the chain goes. >>>UPDATE>>> Jewels are White Sapphire. Still trying to figure out what the base is.
I do know that jewelry with PD on it often means it was crafted with Palladium. Not to mean that your piece is not gold, but that's a signifier that it might be a mixed metal.
A lot of pendents have the gold markings on the bail rather than on the pendent. Take a magnifying glass and check both sides of the loop carefully for markings.