My name is George Hall. My office is located directly across
from a rather large Jewish cemetery in Trevose Pennsylvania.
While walking through the cemetery today I noticed that many of the gravestones had small piles of rocks on top.
Hi George,
You are, probably, not Jewish. When a relative, a friend, etc. visits a Jewish grave, he/she puts a stone or several on the deseased tombstone to say that he/she visited him/her and miss him/her very much. Also that shows to others that the grave was visited.