In alchemical treatises, the formulaL'Oeuvre au Noir designates what is said to be the most difficult phase of the alchemist's process, the separation and dissolution of substance. It is still not clear whether the term applied to daring experiments on matter itself, or whether it was understood to symbolize trials of the mind in discarding all forms of routine and prejudice. Marguerite Yourcenar,The Abyss1
1L'Oeuvre au Noir, or The Work in Black, refers to the first step in alchemy (Nigredo). Itis also the title of the 1968 novel by Belgian-French writer Marguerite Yourcenar, whose English translation by Grace Frick has been published with the under the titles The Abyssor alternately Zeno of Bruges.