13c67163_king___White_Metals_and_Alloys__Reaction_on_Streak
[Possible Alloy] white gold with less than Au 500 (a high precentage of base white metal and silvel) [Further evidence] silver test [Reaction on Streak] 
Attack with brown color and residue
[Ganoksin] Jewelry Making - White Metals and Alloys
Reaction on Streak