An iron shovel is assembled in a Carpentry Shop that has been installed with a carpentry blade. It takes 1 shovel blade and 4 boards to assemble an iron shovel.
Iron shovels are just as effective as slate shovels in hole-digging projects, but they do not break.
Shovels formed on an anvil using blacksmithing are superior to ordinary iron shovels in that they have better hole-digging power. Ordinary iron shovels are cheaper to make, though, and do not need to be shaped on an anvil -- an advantage for those who don't enjoy that activity.
Ordinary shovels can be told apart from blacksmithed shovels (some of which are made of iron) in that blacksmithed shovels have a Quality rating and ordinary iron shovels do not.