The idea of memorialization with stone is ancient and cross-cultural. In some cultures, a simple pebble or stone was left at the gravesite. In others, a pile of rocks might be left, forming a cairn. There are complex structures such as mausoleums, chapels, and palaces constructed out of stone.
Stone has always been a symbol of permanence, hence its prevalence as a material for memorialization.
Common in many cultures is the idea that we imbue the stones with memories. It is not the stone per se which has value, but the memories which we attach to it. It is these memories and the stories we tell which immortalize us.