Silver or white gold casting remains?

[Flyer037]

I was casting in both silver and 18kt white gold a little while ago and, like an idiot, I got some of my sprues and left over metal mixed up and I'm trying to figure out the best way to separate the two. Any thoughts? The ones on the left are definitely silver, the FAR right is definitely gold, but the ones in middle I'm unsure of.

[josef1]

File away some metal, the white gold will be yellower.