fenghuang that would not deign to peck at bird food, but like a Daoist adept, would scorn all but a diet of langgan. This represents a literary transition from glittering fruit of distant Kunlun, to aristocratic fare in golden bowls, eventually to an elixir of immortality. A further extension of the langgan metaphor was to describe natural images of beautiful crystals and lush vegetation. For example, Ban Zhao's poem on "The Arrival of Winter" says, "The long [Yellow River] forms (crystalline) langgan [written langan 瓓玕] / Layered ice is like banked-up jade". Two of Du Fu's poems figuratively used the word langgan in reference to the vegetation around the forest home of a Daoist recluse, and to the splendid grass that provided seating for guests at a royal picnic near a mysterious grotto. Bamboo was the most typical representative of blue-green langgan in the plant world, compare láng 筤 ("bamboo radical" and the liáng phonetic in láng 琅) "young bamboo; blue'" Liu Yuxi wrote that the famous spotted bamboo of South China was "langgan colored". Geographic sources Chinese texts list many diverse locations from where langgan occurred. Several classical works associate mythical langan trees with Kunlun Mountain (far west or northwest China), and two gives sources of actual langgan gemstones, the Shujing says it was tribute from Yong Province (present day Gansu and Shaanxi) and the Guanzi says the Kunlun desert (Xinjiang and Tibet). Official Chinese histories record langgan coming from different sources. The 3rd-century Weilüe, 5th-century Hou Hanshu, 6th-century Wei shu, and 7th-century Liang shu list langgan among the products of Daqin, which depending on context meant the Near East or the Eastern Roman Empire, especially Syria. The Liang shu also says it was found in Kucha (modern Aksu Prefecture, Xinjiang), the 7th-century Jinshu says in Shaanxi, and the 10th-century Tangshu says in India. The Jiangnan Bielu history of the Southern Tang (937–976) says langgan was mined at Pingze 平澤 in Shu (Sichuan Province). The Daoist scholar and alchemist Tao Hongjing (456-536) notes langgan gemstone was traditionally associated with Sichuan. The Tang pharmacologist Su Jing 蘇敬 (d. 674) reports that it came from the distant Man tribes of the Yunnan–Guizhou Plateau and Hotan/Khotan. Accurately identifying geographic sources may be complicated by langgan referring to more than one mineral, as discussed next. Identifications The precise referent of the Chinese name langgan 琅玕 is uncertain in the present day. Scholars have