Also *iwa-gunjō 岩群青. A blue pigment made from pulverized azurite, randōkō 藍銅鉱 or lapis lazuri, seikinseki 青金石; the most important blue pigment used in traditional Japanese painting *nihonga 日本画. Kūjō 空青, mentioned in a Nara period document Shōsōin monjo 正倉院文書 is thought to refer to the same pigment. The shade and tone of the color depends on the purity of the minerals used and the size of the pigment particles; smaller particles give a lighter color. A dark blue color is often called *konjō 紺青 and a blue-green shade gunroku 群緑. Gunjō can be ground finely to give a light blue color called *byakugun 白群. Azurite and lapis lazuri are scarce and expensive, and today a synthetically produced version of gunjō called ultramarine blue is commonly used.