its possibly dmt.. maybe your naphtha evaporated and got saturated and the dmt is precipitating, but since its not soluble in the lye layer, it floats on top between the naphtha and the lye.. you could separate as much as the naphtha as you can, and leave those crystals there where the layers meet, because when you add more fresh (maybe warm) naphtha it should be dissolved.
Next time close the container better so it doesnt evaporate