What is Jifu in Japanese Katana terminology?

Jifu or 地斑 in Japanese, refers to a type of pattern that appears on the surface of the ground iron (jigane) of a Japanese sword. It is one of the effects that appear in the ground skin (jihada). Jifu is a complex pattern that appears along the forged parts of the Mokume (burl) or Itame (wood grain), and it creates a subtle and multi-layered pattern in conjunction with the tempering process.

The term ""Jifu"" is used to describe a state where the ground iron, which has a strong and weak Nie (hard, white particles that form in the steel during the hardening process), changes and becomes a Jifu pattern. This is also referred to as ""Jifu-biri"".

The pattern of the ground iron (jigane) plays a significant role in the aesthetics and value of a Japanese sword. It is one of the factors that sword connoisseurs look at when evaluating a sword. The Jifu, with its complex and multi-layered pattern, is a distinctive feature that sets the sword apart.