Getting sparkle?
 

I have been attempting a lampwork "portrait" of a ruby-throated hummingbird. In order to get some sparkle in the throat, I first tried aventurine in an encased striped stringer with a red F3 core. It looked great as a stringer, but after I took the finished bead out of the kiln, all of the aventurine had turned black. Next I tried dichroic, similarly encased in a striped stringer over red. It's pretty bright, unlike the first, but there is no identifiable sparkle. Any suggestions? Did I burn the aventurine?

Maybe try ground mica. It really pops over darker colors.

I think I might try silver foil under the red or red dichro.

Try using silver dichro and coating it with a red transparent. I've had mixed luck with silver and reds, or perhaps give the silver a thin clear encasement before putting the red on. Reds sometimes react badly to silver, going black or muddy, and need to be kept separate.