i visited sri lanka last year and that is the first time i came across a sandakada pahana or moonstone in english.
this is a semi-circular stone that is seen at the entrance of the temples at anuradhapuram and polonnaruwa.
buddhism flourished during the anuradhapuram. this is when the moonstone was supposed to have developed the most and become the most elaborate with intricate carvings. prior to that it was a square slab of stone.
carved in stone, the moonstone embodies the teachings of buddhism.