My Hampton Bay light fixture (sku 141531) has one white and one black wire (stranded 18AWG) which are a silver color. I tried scratching to see if copper is under some coating, and cut a piece off the end to see if the end showed copper, both with no copper showing. Is there a way to confirm if the wire is copper?
The wire also has a code AWM 3321. Is this telling me that it is tinned copper?

I always thought it was stranded tinned copper also. Haven't ran into aluminum smaller than #14, Here is good info:
Dynamic Surplus A.I.W Corp. White 18AWG 150C 600V AWM Style 3321 Hook-Up Wire QTY: 500'