Langgan

Langgan 琅玕 is the ancient Chinese name of a gemstone which remains an enigma in the history of mineralogy; it has been identified, variously, as blue-green malachite, blue coral, white coral, whitish chalcedony, red spinel, and red jade. It is also the name of a mythological "langgan" tree of immortality found in the western paradise of Kunlun Mountain, and the name of the classic "waidan" alchemical elixir of immortality "langgan huadan" 琅玕華丹 "Elixir Efflorescence of Langgan".
Word.
The Chinese characters 琅 and 玕 used to write the gemstone name "lánggān" are classified as radical-phonetic characters that combine the semantically significant "jade radical" 玉 or 王 (commonly used to write names of jades or gemstones) and phonetic elements hinting at pronunciation. "Láng" 琅 combines the "jade radical" with "liáng" 良 "good; fine" (interpreted to denote "fine jade") and "gān" 玕 combines it with the phonetic "gān" 干 "stem; trunk". The Chinese word "yù" 玉 is usually translated as "jade" but in some contexts translates as "fine ornamental stone; gemstone; precious stone", and can refer to a variety of rocks that carve and polish well, including jadeite, nephrite, agalmatolite, bowenite, and serpentine (Desautels 1977: 81).
Modern written Chinese "láng" 琅 and "gān" 玕 have variant Chinese characters. "Láng" 琅 is occasionally transcribed as "láng" 瑯 (with "láng" 郞 "gentleman") or "lán" 瓓 ("lán" 闌 "railing"); and "gān" 玕 is rarely written as "gān" 玵 (with a "gān" 甘 "sweet" phonetic). "Guwen" "ancient script" variants were "láng" 𤨜 or 𤦴 and "gān" 𤥚.
Berthold Laufer proposed that "langgan" was an onomatopoetic word "descriptive of the sound yielded by the sonorous stone when struck" (1915: 206). "Lang" occurs in several imitative words meaning "tinkling of jade pendants/ornaments": "lángláng" 琅琅 "tinkling/jingling sound", "língláng" 玲琅 "tinkling/jangling of jade", "línláng" 琳琅 "beautiful jade; sound of jade", and "lángdāng" 琅璫 "tinkling sound". Laufer further suggests this etymology would explain the transference of the name "langgan" from a stone to a coral; Du Wan's 杜綰 c. 1125 "Yunlin shipu" 雲林石譜 "Stone Catalogue of the Cloudy Forest" (below) expressly states that the coral "langgan" "when struck develops resonant properties".
Classical descriptions.
The name "langgan" has undergone remarkable semantic change. The first references to "langgan" are found in Chinese classics from the Warring States period (475-221 BCE) and Han dynasty (206 BCE-220 CE), which describe it as a valuable gemstone and mineral drug, as well as the mythological fruit of the "langgan" tree of immortality on Kunlun Mountain. Texts from the turbulent Six Dynasties period (220-589) and Sui dynasty (581-618) used "langgan" gemstone as a literary metaphor, and an ingredient in alchemical elixirs of immortality, many of which were poisonous. During the Tang dynasty (618-907), "langgan" was reinterpreted as a type of coral.
Several early texts (including the "Shujing", "Guanzi", and "Erya" below) recorded "langgan" in context with the obscure gemstone(s) "qiúlín" 璆琳. In Classical Chinese syntax, 璆琳 can be parsed as two "qiu" and "lin" types of jade or as one "qiulin" type. A recent dictionary of Classical Chinese says "qiú" 璆 "fine jade, jade lithophone" is cognate with "qiú" 球 "precious gem, fine jade; jade chime or lithophone" (which later came to mean "ball; sphere"), and "lín" 琳 "blue-gem; sapphire" (Kroll 2017: 374, 272).
In what may be the earliest record (Schafer 1978: 29), the c. 5th-3rd centuries BCE "Yu Gong" "Tribute of Yu the Great" chapter of the "Shujing" "Classic of Documents" says the tributary products from Yong Province (located in the Wei River plain, one of the ancient Nine Provinces) included "qiulin" and "langgan" jade-like gemstones: "Its articles of tribute were the k'ew and lin "gem-stones", and the lang-kan "precious stones"" (tr. Legge 1865 3: 127). Legge quotes Kong Anguo's commentary that "langgan" is "a stone, but like a pearl", and suggests it was possibly lazulite or lapis lazuli, which Laufer calls "purely conjectural" (1915: 205).
The c. 4th-3rd centuries BCE "Guanzi" encyclopedic text, named for and attributed to the 7th century BCE philosopher Guan Zhong, who served as Prime Minister to Duke Huan of Qi (r. 685-643 BCE), uses "bi" 璧 "a flat jade disc with a hole in the center", "qiulin" 璆琳 "lapis lazuli", and "langgan" 琅玕 as examples of how establishing diverse local commodities as fiat currencies will encourage foreign economic cooperation. When Duke Huan asks Guanzi about how to politically control the "Four "Yi"" (meaning "all foreigners" on China's borders), he replies: 
Since the Yuzhi [i.e., Yuezhi/Kushans in Central Asia] have not paid court, I request our use of white jade discs [白璧] as money. Since those in the Kunlun desert (modern-day Xinjiang and Tibet) have not paid court, I request our use of lapis lazuli and "langgan" gems as money. … Since a white jade held tight unseen against one's chest or under one's armpit will be used as a thousand pieces of gold, we can obtain the Yuezhi eight thousand "li" away and make them pay court. Since a lapis lazuli and "langgan" gem (fashioned in) a hair clasp and earring will be used as a thousand gold pieces, we can obtain [i.e., defeat] [the inhabitants] of the Kunlun deserts eight thousand "li" away and make them pay court. Therefore if resources are not commandeered, economies will not connect, those distant from each other will have nothing to use for their common interest and the four "yi" will not be obtained and come to court. (tr. (Lavan et al. 2016: 149; one "li" was approximately one-third mile) 
Xun Kuang's 3rd century BCE Confucian classic "Xunzi" has a context criticizing elaborate burials that uses "dan'gan" 丹矸 (with "dān" 丹 "cinnabar" and "gān" 矸 "waste rock", with the "stone radical" and same "gān" 干 phonetic) and "langgan" 琅玕. 
In these ancient times, the body was covered with pearls and jades, the inner coffin was filled with beautifully ornamented embroideries, and he outer coffin was filled with yellow gold and decorated with cinnabar [丹矸] with added layers of laminar verdite. [In the outer tomb chamber were] rhinoceros and elephant ivory fashioned into trees, with precious rubies [琅玕], magnetite lodestones, and flowering aconite for their fruit." (18.7, tr. Knoblock 1994: 44) 
John Knoblock translates "langgan" as "rubies", noting perhaps the genuine ruby or balas spinel, were connected with the cult of immortality, and cites the "Shanhaijing" saying they grow on Mount Kunlun's Fuchang trees, and the "Zhen'gao" saying that adepts swallow "ruby blossoms" to feign death and become transcendents (1994: 30).
Early Chinese dictionaries define "langgan". The c. 4th-3rd century BCE "Erya" geography section (9 "Shidi" 釋地) lists valuable products from the various regions of ancient China: "The beautiful things of the northwest are the "qiulin" [璆琳] and "langgan" gemstones from the wastelands [虛] of Kunlun Mountain". The 121 CE "Shuowen jiezi" (Jade Radical section 玉部) has two consecutive definitions for "lang" 琅 and "gan" 玕. "Lang" is [used in] "langgan", which "resembles a pearl [似珠者]", "Gan" is [used in] "langgan", paraphrasing the "Yu Gong", "Yong Province [using the ancient "yōng" 雝 character for "yōng" 雍] [produces] "qiulin" and "langgan" [gems] [球琳琅玕]". 
Three sections about western Chinese mountains in the c. 4th-2nd centuries BCE "Shanhaijing" "Classic of Mountains and Seas" record early geographic legends associating "langgan" with Xi Wang Mu "Queen Mother of the West" who lives on Jade Mountain in the mythological axis mundi Kunlun Mountain paradise. Two mention "langgan" gems and one mentions "langganshu" 琅玕樹 trees. The "Shanhaijing" translator Anne Birrell exemplifies the difficulties of translating the word "langgan" in three ways: "pearl-like gems", "red jade", and "precious gem [tree]".
First, the "Classic of the Mountains: West" section says Huaijiang 槐江 (lit. "pagoda-tree river") Mountain, located 400 "li" northeast of Kunlun Mountain, has abundant "langgan" and other valuable minerals. "On the summit of Mount Carobriver are quantities of green male-yellow [多青雄黃]], precious pearl-like gems [藏琅玕], and yellow gold and jade. Granular cinnabar is abundant on its south face and there are quantities of speckled yellow gold and silver on its north face." (2, tr. Birrell 2000: 22). "Male-yellow" overliterally translates "xiónghuáng" 雄黃 "realgar; red orpiment"—Compare Richard Strassberg's translation, "On the mountain’s heights is much green realgar, the finest quality of Langgan-Stone, yellow gold, and jade. On its southern slope are many grains of cinnabar, while on its northern slope are much glittering yellow gold and silver." (2002: 106). Guo Pu's 4th century CE "Shanhaijing" commentary says "langgan" "shi" 石 "stone/gem" (cf. "zi" 子 "seeds" in the third section) resembles a pearl, and "cáng" 藏 "store; conceal, hide" means "yǐn" 隱 "conceal; hide". However, Hao Yixing's 郝懿行 1822 commentary says "cáng" 藏 was originally written "zāng" 臧 "good", that is, Huaijiang Mountain has the "best" quality "langgan".
Second, the "Classic of the Great Wilderness: West" section records that on [Xi] Wang Mu 王母 "Queen Mother [of the West]" Mountain: "Here are the sweet-bloom tree, sweet quince, white weeping willow, the look-flesh creature, the triply-grey horse, precious jade [琁瑰], dark green jade gemstone [瑤碧], the white tree, red jade [琅玕], white cinnabar, green cinnabar, and quantities of silver and iron." (16, tr. Birrell 2000: 174)
Third, the "Classic of Regions Within the Seas: West" section refers to a mythical tricephalic creature dwelling in a "fuchangshu" 服常樹 (lit. "serve constant tree") who guards a "langganshu" tree south of Kunlun: "The wears-ever fruit tree—on its crown there is a three-headed person who is in charge of the precious gem tree [琅玕樹]." (11, tr. Birrell 2000: 141). Interpreters disagree whether the "langgan" tree grows alongside the "fuchang" tree or grows on it (Knoblock 1994: 30). Guo Pu's commentary admits unfamiliarity with the "fuchang" 服常 tree; Wu Renchen's 17th-century commentary notes the similarity with the "shachang" 沙棠 "sand-plum tree" that the "Huainanzi" lists with "langgan", but doubts they are the same. Guo's commentary says "langgan" "zi" 子 "seeds" (Birrell 2000: 249) or "fruits" (Knoblock 1994: 30) resemble pearls (cf. the "Shuowen" definition) and quotes the "Erya" that it is found on Kunlun Mountain.
The c. 120 BCE "Huainanzi" "Terrestrial Forms" chapter (4 墬形) describes "langgan" trees and "langgan" jade both found on Mt. Kunlun. The first context describes how Yu the Great controlled the Great Flood and "excavated the wastelands of Kunlun [昆侖之球] to make level ground". "Atop the heights of Kunlun are treelike cereal plants [木禾] thirty-five feet tall. Growing to the west of these are pearl trees [珠樹], jade trees [玉樹], carnelian trees [琁樹], and no-death trees [不死樹]. To the east are found sand-plum trees [沙棠] and malachite trees [琅玕]. To the south are crimson trees [絳樹]. To the north are "bi" jade trees [碧樹] and "yao" jade trees [瑤樹]." (4.3, tr. Major et al. 2010: 159; translating with Schafer's "malachite" instead of "coral"). The second context paraphrases the "Erya" definition (above) of "langgan": "The beautiful things of the northwest are the "qiu", "lin", and "langgan" jades [球琳琅玕] of the Kunlun Mountains [昆侖]" (4.7, tr. Major et al. 2010: 159; noting that "qiu", "lin", and "langgan" are "types of jade, mostly not identifiable with certainty").
Medicine.
Several early classics of traditional Chinese medicine mention "langgan".
The c. 1st century BCE "Huangdi Neijing"'s "Suwen" 素問 "Basic Questions" section uses "langgan" beads to describe a healthy pulse. "When man is serene and healthy the pulse of the heart flows and connects, just as pearls are joined together or like a string of red jade [如循琅玕]—then one can speak of a healthy heart" (tr. Veith 1949: 173).
The c. 2nd century CE "Nan Jing" explains this "langgan" bead simile: "[If the "qi" in] the vessels comes tied together like rings, or as if they were following [in their movement a chain of] "lang gan" stones [如循琅玕], that implies a normal state." Commentaries elaborate that "langgan" stones "resemble pearls" and their movement is like a "string of jade- or pearl-like beads" (tr. Unschuld 2016: 179). 
The c. 3rd century CE "Shennong Bencaojing" lists "qīng lánggān" 青琅玕 "blue-green "langgan"" or "shízhū" 石珠 (lit. "rock pearl") as a mineral drug used to treat ailments such as itchy skin, carbuncle, and ALS. This is one of the rare early references to "langgan" that treats it as a real substance, while many others make it a feature of the divine world (Schafer 1978: 27).
Alchemy.
The "langgan huadan" 琅玕華丹 "Elixir Efflorescence of Langgan" name of the "waidan" "external alchemy" elixir of immortality is the best-known usage of the word "langgan" (Pregadio 2008: 605). Some other translations are "Elixir of Langgan Efflorescence" (Strickmann 1979: 135, Bokenkamp 1997: 190),"Lang-Kan (Gem) Radiant Elixir" (Needham et al. 1980: 217), and "Elixir Flower of Langgan" (Pregadio 2006: 7). 
The earliest method of compounding the elixir is found in the "Taiwei lingshu ziwen langgan huadan shenzhen shangjing" 太微靈書紫文琅玕華丹神真上經 "Supreme Scripture on the Elixir of Langgan Efflorescence, from the Purple Texts Inscribed by the Spirits of Grand Tenuity" (translated by Bokenkamp 1997: 331-339). This text was originally part of the Daoist Shangqing School scriptural corpus supposedly revealed to Yang Xi (330-c. 386 CE) between 364 and 370 (Komjathy 2004: 23-24).
The Purple Texts alchemical recipe for preparing Elixir of "Langgan" Efflorescence involves nine steps in four stages carried out over thirteen years. The first stage produces the "Langgan" Efflorescence proper, which when ingested is said to make "one's complexion similar to gold and jade and enables one to summon divine beings". The next three stages further refine and transform the "Langgan" Elixir, repeatedly plant it in the earth, and eventually generate a tree whose fruits confer immortality when eaten, just like those of the legendary "langgan" tree on Mount Kunlun (Pregadio 2008: 605). Upon completing any of the nine successive steps in producing the elixir, the alchemist (or adept in the "neidan" interpretation) can choose to either ingest the products and obtain immortality by ascending into the realm of Shangqing heavens or may continue on to the next step with the promise of ever-increasing rewards (Bokenkamp 1997: 290).
The first stage has one complex "waidan" step of compounding the primary "Langgan" Efflorescence. After performing ritual "zhāi" 齋 "purification practices" for 40 days, the adept spends 60 days to acquire and prepared the elixir's fourteen ingredients, place them in a crucible, add mercury on top of them, lute the crucible with several layers of mud, and after sacrificing wine to the divinities, heating the crucible for 100 days. The elixir's fourteen reagents, given in exalted code names such as "White-Silk Flying Dragon" for quartz, are: cinnabar, realgar, milky quartz, azurite, amethyst, graphite, saltpeter, sulfur, asbestos, mica, iron pyrite, lead carbonate, Turkestan salt (desert lake precipitates containing gypsum, anhydrite, and halite), and orpiment (Bokenkamp 1997: 334). Based upon these ingredients, Schafer says the end product was probably bluish flint glass with a high lead content (1978: 37). The alchemist can either leave the crucible closed and proceed to the next stage or break it open and consume the "langan" elixir that is said to yield marvelous results. 
The efflorescence should have thirty-seven hues. It is a volatile liquid both brilliant and mottled, a purple aurora darkly flashing. This is called the Elixir of "Langgan" Efflorescence. If, just at dawn on the first day of the eleventh, fourth, or eighth month, you bow repeatedly and ingest one ounce of this elixir with the water from an east-flowing stream, seven-colored pneumas will rise from your head and your face will have the jadelike glow of metallic efflorescence. If you hold your breath, immediately a chariot from the eight shrouded extents of the universe will arrive. When you spit on the ground, your saliva will transform into a flying dragon. When you whistle to your left, divine Transcendents will pay court to you; when you point to the right, the vapors of Three Elementals will join with the wind. Then, in thousands of conveyances, with myriad outriders, you will fly up to Upper Clarity. (tr. Bokenkamp 1997: 336) 
The second stage comprises two iterative 100-day "waidan" alchemical steps transforming the elixir. Firing the unopened stage one crucible of "Langgan" Efflorescence for another 100 days will produce the Lunar Efflorescence of the Yellow Solution [黄水月華], which when consumed will make you "change forms ten thousand times, your eyes will become luminous moons, and you will float above in the Grand Void to fly off to the Palace of Purple Tenuity". The next step of firing the closed crucible for an additional one 100 days will produce three giant pearls called the Jade Essence of the Swirling Solution [徊水玉精]. Ingesting one alchemical pearl supposedly causes you to immediately give off liquid and fire, form gems with your breath, and your body "will become a sun, and the Thearchs of Heaven will descend to greet you. You will rise as a glowing orb to Upper Clarity." (tr. Bokenkamp 1997: 336-337).
The third stage involves four 3-year steps utilizing the elixirs produced in the first two stages to create fantastic seeds that are replanted and grow into increasingly perfected "spirit trees" with fruits of immortality. This stage falls between conventional "waidan" alchemy and the horticultural art of growing marvelous "zhi" 芝 "plants of longevity; fungi" such as the lingzhi mushroom (Needham et al. 1980: 217). Initially, the adept mixes the Elixir of "Langgan" Efflorescence with Jade Essence of the Swirling Solution, transforming the "jīng" 精 "essence; sperm; seed" in the latter name into an actual seed that is planted in an irrigated field. After three years it grows into the Tree of Ringed Adamant [環剛樹子] or Hidden Polypore of the Grand Bourne [太極隱芝], which has a ring-shaped fruit like a red jujube. Next, the adept plants one of the ringed fruits and waters it with the Yellow Solution, and after three years a plant called the called the Phoenix-Brain Polypore ["fengnao zhi" 鳳腦芝] will grow like a calabash, with pits like five-colored peaches. Then, a phoenix-brain fruit is planted and watered with Yellow Solution, which after three years will grow into a red tree, like a pine, five or six feet in height, with a jade-white fruit like a pear [赤樹白子]. Lastly, the adept plants the seed of the red tree, waters it with Swirling Solution, waits another three years for the growth of a vermilion tree like a plum, six or seven feet in height, with a halycon-blue fruit like the jujube [絳樹青實]. Upon eating this fruit, the adept will ascend to the heaven of Purple Tenuity. (tr. Bokenkamp 1997: 337-338).
The fourth stage involves two comparatively quicker "waidan" steps. The adept repeatedly boils equal parts of the Yellow Solution and the Swirling Solution, and transforms them into the Blue Florets of Aqueous Yang [水陽青映]. If you drink this at dawn, your body will issue a blue and gemmy light, your mouth will spew forth purple vapors, and you will rise above to Upper Clarity ["Shangqing"]. But before departing earth, the adept's last step is to mix the remaining Elixir of Langan Efflorescence with liquified lead and mercury to produce 50-pound ingots of alchemical silver and purple gold, make incantations to the water spirits, and throw both oblatory ingots into a stream (tr. Bokenkamp 1997: 338-339).
Despite the carefully detailed Purple Texts' "waidan" recipe for preparing "langgan" elixirs, scholars have doubted that the authors actually meant for it to be produced and consumed. Some interpret the impractical 13-year elixir recipe as symbolic instructions for what later came to be known as "neidan" meditative visualization, and is more a "product of religious imagination", drawing on the respected metaphors of alchemical language, than a laboratory manual drawing on the metaphors of meditation (Bokenkamp 1997: 295). Others believe this "extravagantly impractical recipe" is an attempt to assimilate into conventional "waidan" alchemy the ancient legends about "langgan" gems that grow on trees in the paradise of KunIun (Needham et al. 1980: 217).
The Shangqing Daoist patriarch Tao Hongjing compiled and edited both the c. 370 "Taiwei lingshu ziwen langgan huadan shenzhen shangjing" and the c. 499 "Zhen'gao" 真誥 "Declarations of the Perfected" that also mentions "langan" elixirs in some of the same terminology. One context records that the early Daoist masters Yan Menzi 衍門子, Gao Qiuzi 高丘子, and Master Hongyai 洪涯先生 swallowed "langgan hua" 琅玕華 "langgan blossoms" to feign death and become "xian" transcendents and enter the "dark region" beyond the world. Needham and Lu proposed this "langgan hua" probably refers to a red or green poisonous mushroom (1974: 296), and Knoblock surmised that these "ruby blossoms" were a species of hallucinogenic mushroom connected with the elixir of immortality (1994: 30). Another "Zhen'gao" context describes how in the Shangqing latter days before the apocalypse (predicted to be in 507) people will practice alchemy to create immortality drugs, including the "Langgan" Elixir that "will flow and flower in thick billows" and Cloud "Langgan". If the adept takes one spatula full of elixir, "their spiritual feathers will spread forth like pinions. Then will they (be able to) peruse the pattern figured on the Vault of Space, and glow forth in the Chamber of Primal Commencement" (tr. Needham et al. 1980: 216).
Several ingredients in the Elixir of "Langgan" Efflorescence are toxic heavy metals including mercury, lead, and arsenic, and alchemical elixir poisoning was common knowledge in China. Academics have puzzled over why Daoist adepts would knowingly consume a compound of mineral poisons, and Michel Strickmann, a scholar of Daoist and Buddhist studies, proposes that "langgan" elixir was believed to be an agent of self-liberation that guaranteed immortality to the faithful through a kind of ritual suicide. Since early Daoist literature thoroughly, "even rapturously", described the deadly toxic qualities of many elixirs, Strickmann concluded that scholars need to reexamine the Western stereotype of "accidental elixir poisoning" that supposedly applied to "misguided alchemists and their unwitting imperial patrons" (1979:191).
Literature.
Chinese authors extended the classical descriptions of "langgan" meaning "a highly valued gem from western China; a mythical tree of immortality on Kunlun Mountain" into a literary and poetic metaphor for the exotic beauties of an idealized natural world. 
Several early writers described "langgan" jewelry, both real and fictional. The 2nd-century scholar and scientist Zhang Heng described a party for the Han nobility at which guests were delighted with the presentation of bowls overflowing with "zhēnxiū" 珍羞 "delicacies; exotic foods" including "langgan" fruits of paradise. The 3rd-century poet Cao Zhi described hanging "halcyon blue" ("cuì" 翠) "langgan" from the waist of his "beautiful person", and the 5th-century poet Jiang Yan adorned a goddess with gems of "langgan". Some other authors reinforced use of its name to refer to divine fruits on heavenly trees. Ruan Ji, one of the Seven Sages of the Bamboo Grove, wrote a 3rd-century poem titled "Dining at Sunrise on Langgan Fruit". The 8th-century poet Li Bai wrote about a famished but proud "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 (Schafer 1978: 30).
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 (Schafer 1978: 31). 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'" (Schafer 1978: 32). Liu Yuxi wrote that the famous spotted bamboo of South China was ""langgan" colored" (Schafer 1965: 545).
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) (Laufer 1915: 205). 
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 (Schafer 1978: 29-30). 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 described it as an "enigmatic archaism of politely pleasant or poetic usage" (Schafer 1961: 41), and "one of the most elusive terms in Chinese mineralogy" (Needham and Lu 1974: 296). Identifications of "langgan" comprise at least three categories: Blue-green "langgan" was first recorded circa 4th century BCE, Coral "langgan" from the 8th century, and Red "langgan" is from an uncertain date.
Edward H. Schafer, an eminent scholar of Tang dynasty literature and history, discussed "langgan" in several books and articles. His proposed identifications gradually changed from Mediterranean red coral (1961), to coral or a glass-like gem (1963), to chrysoprase or demantoid (1965), to coral or red spinel (1967), and ultimately to malachite (1978).
Blue-green "langgan".
"Langgan" was a "qīng" 青 "green; blue; greenish black" (see Blue–green distinction in language) gemstone of lustrous appearance mentioned in numerous classical texts. They listed it among historical imperial tribute products presented from the far western regions of China, and as the mineral-fruit of the legendary "langgan" trees of immortality on Mount Kunlun (Bokenkamp 1997: 289). 
Schafer's 1978 monograph on "langgan" sought to identify the treasured blue-green gemstone, if it ever had a unique identity, and concluded the most plausible identification is malachite, a bright green mineral that was anciently used as a copper ore and an ornamental stone. Two early Chinese mineralogical authorities (Chang 1921: 24, Read and Pak 1928: 21) identified "langgan" as malachite, commonly called "kǒngquèshí" 孔雀石 (lit. "peacock stone") or "shílǜ" 石綠 (lit. "stone green").
Comparing blue-green stones that were known in early East Asia, Schafer disqualified several conceivable identities; demantoid garnet and green tourmaline are rarely of gem quality, while neither apple-green chrysoprase nor light greenish-blue turquoise typically have dark hues. This leaves malachite,
This handsome green carbonate of copper has important credentials. It is often found in copper mines, and is therefore regularly at the disposal of copper- and bronze-producing peoples. It has, in certain varieties, a lovely silky luster, caused by its fibrous structure. It is soft and easily cut. It takes a good polish. It was commonly made into beads both in the western and eastern worlds. Above all, even uncut malachite often has a nodular or botryoidal structure, like little clumps of bright green beads, one of the classical forms attributed to "lang-kan". Sometimes, too, it is stalactitic, like little stone trees. (1978: 33) 
Furthermore, archeology confirms that malachite was an important gemstone of pre-Han China. Inlays of malachite and turquoise decorated many early Chinese bronze weapons and ritual vessels (MOMA 1980: 38, 188).
Tang sources continued to record blue-green "langgan". Su Jing's 652 "Xinxiu bencao" 新修本草 said it was a glassy substance similar to "liúli" 琉璃 "colored glaze; glass; glossy gem" that was imported from the Man tribes in the Southwest and from Khotan (Schafer 1963: 246). In 762, Emperor Daizong of Tang proclaimed a new era name of Baoying 寶應 "Treasure Response" in honor of the discovery of thirteen auspicious treasures in Jiangsu, one of which was glassy "langgan" beads (1965: 545-546).
Coral "langgan".
Tang dynasty herbalists and pharmacists changed the denotation of "langgan" from the traditional blue-green gemstone to a kind of coral. Chen Cangqi's c. 720 "Bencao shiyi" 本草拾遺 "Collected Addenda to the Pharmacopoeia" described it a pale red coral, growing like a branched tree on the bottom of the sea, fished by means of nets, and after coming out of the water gradually darkens and turns blue (Schafer 1963: 246; 1967: 159).
"Langan" already had an established connection with coral. Chinese mythology matches two antipodean paradises of Mount Kunlun in the far west and Mount Penglai located on an island in the far eastern Bohai Sea. Both mountains had mythic plants and trees of immortality that attracted Daoist "xian" transcendents; Kunlun's red "langgan" trees with blue-green fruits were paralleled by Penglai's "shanhu shu" 珊瑚樹 "red coral trees" (Schafer 1963: 246).
Regarding what variety of blue or green branching coral was identified as this "mineralized subaqueous shrub" "langgan". Since it must have been a coral attractive enough to be comparable with the extravagant myths of Kunlun, Schafer suggests considering the blue coral "Heliopora coerula". It is the only living species in the family Helioporidae, the only octocoral known to produce a massive skeleton, and was found throughout Pacific and Indian Oceans, although the IUCN currently considers it a vulnerable species (1978: 32).
Du Wan's c. 1124 "Yunlin shipu" mineralogy book has a section (100) on "langgan shi" 琅玕石 that mentions "shanhu" "coral". 
A coral-like stone found in shallow water along the coast of Ningbo Zhejiang. Some specimens are two or three feet high. They must be pulled up by ropes let down from rafts. Though white when first taken from the water, they turn a dull purple after a while. They are patterned everywhere with circles, like ginger branches, and are rather brittle. Though the natives hold … (tr. Schafer 1961: 94-95). 
Li Shizhen's 1578 "Bencao Gangmu" classic pharmacopeia objects to applying the term "langgan" to these marine invertebrates, which should properly be called "shanhu" while "langgan" should only be applied to the stone occurring in the mountains. Li's commentary suggests that the terminological confusion arose from the "Shuowen jiezi" definition of "shanhu" 珊瑚: 色赤生於海或生於山 "coral is red colored and grows in the ocean or in the mountains". This puzzling description of mountain corals was more likely a textual misunderstanding than a reference to coral fossils (Laufer 1915: 205).
Red "langgan".
The most recent, and least historically documented, identification of "langgan" is a red gemstone. The Chinese geologist Chang Hung-Chao (Zhang Hongzhao) propagated this explanation when his book about geological terms in Chinese literature identified "langgan" as malachite, and noted an alternative construal of reddish spinel or balas ruby from the famous mines at Badakhshan (1921: 26-27, 24). Some authors have cited Chang's balas ruby identification of "langgan" (e.g., Needham and Lu 1974: 180); others have used, or even confused, it with ruby, in translations (e.g., "precious rubies" Knoblock 1994: 44).
However, Schafer demonstrates that Chang's "supposed" textual evidence for red "langgan" is tenuous and suggests that Guo Pu's "Shanhai jing" commentary created this mineralogical confusion. Guo glosses the "langgan" tree as red, but is unclear whether this refers to the tree itself or its gem-like fruit. Compare Birrell's and Bokencamp's "Shanhai jing" translations of "red jade" and "green kernels from scarlet gem trees" (2000: 174; 1997: 312). Chang misquotes "dan'gan" 丹矸 "cinnabar rock" from the "Xunzi" as "dan'gan" 丹玕 "cinnabar "gan"", and cites one textual occurrence of the term. The Shangqing Daoist "Dadong zhenjing" 大洞真經 Authentic Scripture of the Great Cavern records a heavenly palace named Dan'gan dian 丹玕殿 Basilica of the Cinnabar "Gan". Admitting the possibility of interpreting "gan" 玕 as a monosyllabic truncation for "langgan" 琅玕, comparable with reading "hongpo" 红珀 for "honghupo" 红琥珀 "red amber", Schafer concludes there is insufficient "dan'gan" evidence for an explicit red variety of "langgan" (1978: 28). 
The lyrical term "langgan" occurs 87 times in the huge "Quan Tangshi" collection of Tang poetry, with only two "hong langgen" 紅琅玕 "red "langgan"" usages by the Buddhist monk-poets Guanxiu (831-912) and Ji Qi 齊己 (863-937). Both poems use "langgan" to describe "red coral", the latter (贈念法華經) uses "shanhu" in the same line: 珊瑚捶打紅琅玕 "coral beating on red "langgan"" in cold waters.
Dictionary translations.
Chinese-English dictionaries illustrate the multifaceted difficulties of identifying "langgan". Compare the following list.
Most of these bilingual Chinese dictionaries cross-reference "lang" and "gan" to "langgan", but a few translate "lang" and "gan" independently. In terms of Chinese word morphology, "láng" 琅 is a free morpheme that can appear alone (for instance, a surname) or in other compound words (such as "fàláng" 琺琅 "enamel" and "Lángyá shān" 琅琊山 "Mount Langya (Anhui)") while "gān" 玕 is a bound morpheme that only occurs in the compound "lánggān" and does not have independent meaning.
The origin of Giles' "lang" translation "a kind of white carnelian" is unknown, unless it derives from Williams' "a whitish stone". It was copied in Mathews' and various other Chinese dictionaries up to the online standard Unihan Database "a variety of white carnelian; pure". "White carnelian" is a marketing name for "white or whitish chalcedony of faint carnelian color" (Manutchehr-Danai 2000: 507). Carnelian is usually reddish-brown while common chalcedony colors are white, grey, brown, and blue.