Hammerscale

The flakes can vary greatly in appearance and size; however, their color ranges from a dark black to a lustrous blue or grey and their thickness from one to five millimeters.

[4] Ultimately, some still argue that the chemical components of hammerscale besides iron vary widely beyond ionized oxygen to form a metal oxide.

The scale produced at this stage is characterized by its blue-black color and tends to be slimmer and darker due to its high iron oxide content.

[7][circular reference] Due to the high volume of hammerscale flakes and spheroid shells produced during regular ironworking processes, archaeologists often use its presence to identify iron smithies and smelters.

[10][11] Beyond the distribution, the chemical composition and physical characteristics of specific samples of hammerscale can aid archaeologists in determining the purpose of an ironworking feature.

In particular, certain samples, such as spheroidal hammerscale, are only produced during certain earlier stages of the iron purification process, providing evidence of smelting activities.

[12] Due its small size and often darker color, hammerscale is difficult to discover while carrying out simple archaeological processes, such as dry or wet sieving.

This is still a rare practice for lack of time or expertise, but nevertheless recommended and if untenable, soil samples should still be run over with a magnet so as to collect hammerscale flakes on site.

[6][10][12][13] The earliest mention of hammerscale in an archaeological context derived from a 1941 study of Roman-built fort in Great Britain, located on Hadrian’s wall.

For example, in an excavation in 1992, by means of establishing a grid and collecting local samples, the former location of a hearth and an anvil was determined despite the lack of the direct remains of either.

[1] Arne Jouttijärvi writes of three sites at which hammerscale deposits and concentration were used to map the areas of smithies in Viking Age pithouses in modern-day Denmark and Norway.