Definatly not a Military headstone- Calvery is where Christ died, Cavalry are mounted soldiers:-)

The 13th held a lot of Jones's
Co. "L" had
John B. age 19
John W. age 19
Joshua age 18
William C. age 18

Co. "G" included
James age 18
John age 19

Co. "C"
William H. age 31
William age 45(!)rare age for a soldier of the time

and Co. "B" included a John Jones, Age 37(again somewhat rare)

Co. "F" had Henry T. Jones, age 18

Looks like the kids enlisted in different companies from the parents. Bet they had some high times together.