Palladium is usually used as an allow in some jewelry, it really didn't start getting popularity until a few years ago. When allowed with gold it turns white/gray and is usually marked. Some jewelry in the last 3 years has been made from an alloy called Palladium 950 that is 95% palladium and the other 5% as a hardener, usually iridium.
Basic fact is unless you process it there is no way of knowing. Or unless its marked as such, But keep in mind for years PD was only $50 to $100 per ounce until it spiked a few years back to over a grand an ounce, And of course now its going up in value.
PD is a darker gray in color than nickel or normal white gold, and darker than silver.
