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".

[3] In what may be the earliest record,[4] 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".

[5] 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".

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.

[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."

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".

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.

[16] 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."

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.

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.

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.

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.

[31] 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.

[32] 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.

[21] 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.

[35] 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.

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 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.

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.

[46] 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.

[47] Schafer's 1978 monograph on langgan[46] 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.

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.

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.

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.

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".

[8] 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.

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.