Activities: Toddler, Seventh Generation

Crystals in Diaper

My 5 month old daughter frequently has crystals in her diaper (they look like large pieces of salt.) I have read online that this is normal for the first few months of life in breastfed babies (she is), but she is now 5 months. I asked our ped and she asked if her urine was ever dark (it isn't) and if it could be a piece of diaper (it most clearly is not). Has anyone else experienced this? We are using seventh generation diapers.