Until Mao, if he wishes to, shows up to gives us more details about Jindan here is a nice article: Jindan (Golden Elixir) - From The Encyclopedia of Taoism
Authors of alchemical texts often call their tradition the Way of the Golden Elixir (jindan zhi dao ).
Gold (jin ) represents the state of constancy and immutability beyond the change and transiency that characterize the manifested world.
As for dan , or “elixir,” lexical analysis shows that the semantic field of this term — which commonly denotes a variety of red — evolves from a root-meaning of “essence,” and that its connotations include the reality, principle, or true nature of an entity, or its most basic and significant element, quality, or property.
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Chen Zhixu and other authors emphasize that the inner elixir is possessed by every human being, and is a representation of one’s own innate realized state. Liu Yiming (1734-1821) expresses this notion as follows:
Human beings receive this Golden Elixir from Heaven. . . .
Golden Elixir is another name for one’s fundamental nature, formed out of primeval inchoateness (huncheng, a term derived from the Daode jing). There is no other Golden Elixir outside one’s fundamental nature. Every human being has this Golden Elixir complete in himself: it is entirely realized in everybody. It is neither more in a sage, nor less in an ordinary person. It is the seed of Immortals and Buddhas, and the root of worthies and sages. (Wuzhen zhizhi, chapter 1)
Beautiful field