青貝微塵塗 Aogai Mijin-nuri

What is Aogai Mijin-nuri in Japanese Katana terminology

The term "青貝微塵塗" (Aogai Mijin-nuri) refers to a decorative technique where the shell of a mollusk from the Turbinidae family, known as "Aogai" or "blue shell", is finely crushed and embedded in lacquer, then polished. The inside of the Aogai shell has a bluish iridescence, which has been used as a decorative material since ancient times. In addition to Aogai, the shells of luminescent shells and abalone are sometimes used. Among the many materials used to create patterns, it has a distinct glamour different from metal.