Nephrite such as Lantian, Shaanxi, were also in great demand). There, white and greenish nephrite jade is found in small quarries and as pebbles and boulders in the rivers flowing from the Kuen-Lun mountain range northward into the Takla-Makan desert area. River jade collection was concentrated in the Yarkand, and the White Jade (Yurungkash) and Black Jade (Karakash) Rivers in Khotan. From the Kingdom of Khotan, on the southern leg of the Silk Road, yearly tribute payments consisting of the most precious white jade were made to the Chinese imperial court and there transformed into "objets d'art" by skilled artisans, as
Theory of forms admitted were impossible to know. Nevertheless, he formulated a very specific description of that world, which did not match his metaphysical principles. Corresponding to the world of Forms is our world, that of the shadows, an imitation of the real one. Just as shadows exist only because of the light of a fire, our world exists as, "the offspring of the good". Our world is modeled after the patterns of the Forms. The function of humans in our world is therefore to imitate the ideal world as much as possible which, importantly, includes imitating the good, i.e. acting morally. Plato