Stones are for Markers

"12 Then Samuel took a stone, and set it between Mizpeh and Shen, and called the name of it Ebenezer, saying, Hitherto hath the Lord helped us."

1 Samuel 7:12

No tool of iron

"And if thou wilt make me an altar of stone, thou shalt not build it of hewn stone: for if thou lift up thy tool upon it, thou hast polluted it."

Exodus 20:25