Purity - White sparks...?

[Arcanex]

SWIM bought an eighth of some very nice bud a couple of weeks ago, and noticed that the joint was sporadically producing small showers of white sparks.

If this had happened shortly after lighting it SWIM would have put it down to the lighter, but it happened at random tokes throughout the joint.

It wasn't very frequent, but it was very noticable. All of the other joints that SWIM made out of that eighth were fine.

I'm guessing SWIM must have unknowingly introduced something sparkly into the joint while rolling it, but SWIM has no idea how.
Perhaps there could have been something on the scissors that SWIM used to shred up the bud, but that seems unlikely, since those scissors were used to roll several joints before the sparkly one.

Does anyone have any idea what it may have been?