If the baby fills the diaper too much with urine, then the diaper sometimes opens and these little soft crystals come out. Maybe that’s what you’re seeing?
I would think the same as Andrea, unless there was only a small amount of urine in the diaper.
My first guess would be dehydration? I think it’s actually more common to see urate crystals with newborns. I’d just call the pediatrician and ask.
If the baby fills the diaper too much with urine, then the diaper sometimes opens and these little soft crystals come out. Maybe that’s what you’re seeing?