What is Jigane in Japanese Katana terminology?

Jigane or 地鉄 in Japanese, refers to the ground iron of a Japanese sword. It is the base material of the sword, which is revealed as a result of the ""Orimodoshi Tanren"" (折返し鍛錬), a process of repeated folding and forging. The pattern that appears on the surface of the ground iron as a result of this process is called ""Jihada"" (地肌).

The method of forging a Japanese sword varies depending on the era and the school of the swordsmith, and therefore, the appearance of the Jihada also varies. This makes the Jihada one of the key points in appreciating Japanese swords.

The Jihada can be broadly classified into Itame (板目), Mokume (杢目), Masame (柾目), and Ayasugi (綾杉). However, it is common for these patterns to appear in a combined state.

- Itame (板目): This pattern resembles the grain of wood planks.
- Mokume (杢目): This pattern resembles the grain of burl wood.
- Masame (柾目): This pattern appears as straight lines, resembling the grain of straight-grained wood.
- Ayasugi (綾杉): This pattern resembles the grain of cedar wood, appearing in a wave-like pattern.

Each of these patterns is a testament to the skill and craftsmanship of the swordsmith, and they are one of the distinctive features that set Japanese swords apart.