Yes...the typical composition of old square nails is significantly different compared to modern round nails and they sometimes show as a good target.
When the ore was smelted to make square nails, little to no separation of the different types of metal alloys was completed. The ore often went from the ground to the nail; every type of metal that was in the ore is in the square nail. So as square nails age, the iron corrodes away leaving behind all the noble non-ferrous metals like copper. So the longer in the ground or the older a square nail is, the better it looks to a metal detector.
In ore processing most all the different noble metal are present to some degree or another in trace amounts. For modern round nails, the smelting process is much more elaborate. They separate and keep all the noble metals for resale at much better prices. You really are getting only iron in a round nail. As the iron corrodes away, noble metals are not there to make the signal better with age. However, the signal is so strong and polarized (magnetically) it can often still be difficult to reject.
Square nails are more difficult to reject compared to round nails, as the noble metals within the square nails alloy enhance the square nail signal both with and without age.
In summary, square nails are mostly iron with whatever other metals were in the ore. Round Nails are just iron.
When the ore was smelted to make square nails, little to no separation of the different types of metal alloys was completed. The ore often went from the ground to the nail; every type of metal that was in the ore is in the square nail. So as square nails age, the iron corrodes away leaving behind all the noble non-ferrous metals like copper. So the longer in the ground or the older a square nail is, the better it looks to a metal detector.
In ore processing most all the different noble metal are present to some degree or another in trace amounts. For modern round nails, the smelting process is much more elaborate. They separate and keep all the noble metals for resale at much better prices. You really are getting only iron in a round nail. As the iron corrodes away, noble metals are not there to make the signal better with age. However, the signal is so strong and polarized (magnetically) it can often still be difficult to reject.
Square nails are more difficult to reject compared to round nails, as the noble metals within the square nails alloy enhance the square nail signal both with and without age.
In summary, square nails are mostly iron with whatever other metals were in the ore. Round Nails are just iron.
wacko