Many times when visiting an older cemetery or undertaking a clean up and restoration project you will find numerous rocks located within that cemetery. While these rocks may look to be at first glance just randomly scattered rocks, in reality they often are the only marker or indication that this is in fact the location of a grave. A general rule to follow is that you should never remove a rock from a cemetery.
The use of rocks as grave markers can be for any number of reasons. Some of these include:
Many people could not afford to purchase a carved gravestone. Often times in these cases "field stones" or other such rocks were used in place of a carved marker. During the depression years there was no money to purchase gravestones and it seems over the years no one has stepped up to replace the stones. Still more cemeteries will often have rows of graves with "field stone" markers. Many times graves were marked by non-native rocks (all others having been removed from the immediate vicinity) so that others would know a grave existed. Often times a larger rock was placed at the head of the grave and a smaller one at the foot. Later, if a traditional tombstone was placed, the rock was removed at the time the marker was erected. Some have long flat rocks placed in the ground in a perpendicular fashion to resemble the regular gravestones but some are marked with just a rock.
Local Customs - While the grave itself may or may not have been marked by a rock, with many of the older burial sites it was a custom to outline the grave with a border of rocks. This custom may have arisen from local customs of using field rocks to outline fields, or build cairns for property corner markers.
Lack of a local stone mason at the time.
In some cases there rocks have been removed by workers in order to make mowing easier. All too often we are discovering that a Boy Scout troop or a 4-H group did a community service project and removed all the "loose" rocks from the cemeteries. It is also possible if you find a pile of rocks in the area of a neglected or abused cemetery that someone before you removed them from graves, and piled them where you are finding them.
In the very old cemeteries in the desert west, a wooden cross was placed at the head of the grave and the grave outlined in small rocks. It didn't take long for the sand to cover the small rocks and for the wooden cross to deteriorate. So, if anyone discovers a line of small rocks in or under the sand, look for the grave!