Nigredo

1. Etymology

Nigredo (alchemy: the blackening) corresponds psychologically to mental disorientation that typically arises while assimilating unconscious contents—particularly aspects of the shadow. Related: melancholia; “black raven.”

2. Plain summary

Even moderately comprehensive shadow-knowledge can produce confusion and mental darkness Jung never remotely imagined beforehand. Alchemists called this nigredo melancholia—“a black blacker than black,” night, affliction of the soul, confusion—or the black raven (for the adept, a serious allegory, not a joke).

Samuels (alchemy glossary): darkening of the elements suggesting something of import is about to take place; in analysis may appear as depression just prior to movement, or the end of an initial honeymoon period; in general, confrontation with the shadow.

Examples (exhaustive house list for this Index lemma — common nigredo motifs named across Jung’s essays and standard Jungian lexica; not a claim that Jung’s CW contains only these):
alchemical blackening; mental disorientation; assimilating unconscious / shadow; melancholia / black raven; depression before movement; end of honeymoon period; personality problems newly imagined; opus stage toward individuation.

3. Academic elucidation

In analytical psychology nigredo is alchemical figure for shadow-assimilation darkness—CW 14. Descent Press keeps Sharp and Samuels (alchemy ~p. 14) in §4. Prefer CW 14 ¶741.

4. Lexicon

Sharp (1991)

Nigredo. An alchemical term, corresponding psychologically to the mental disorientation that typically arises in the process of assimilating unconscious contents, particularly aspects of the shadow. … the alchemists called their nigredo melancholia, "a black blacker than black," night, an affliction of the soul, confusion, etc., or, more pointedly, the "black raven."

(Sharp, 1991) — cites CW 14 ¶741 in Sharp’s lemma.

Samuels, Shorter & Plaut (1986) — alchemy glossary Nigredo p. 14

Nigredo: Stage in the alchemical process, a darkening of the elements suggesting that something of import is about to take place. In analysis, may take the form of a depression just prior to movement or the end of an initial, honeymoon period. In general, refers to confrontation with the SHADOW.

(Samuels, Shorter, & Plaut, 1986/2013, p. 14)

5. CW concordance — sample, not exhaustive

Self-knowledge is an adventure that carries us unexpectedly far and deep. Even a moderately comprehensive knowledge of the shadow can cause a good deal of confusion and mental darkness, since it gives rise to personality problems which one had never remotely imagined before.
(Jung, 1955–1956/1970, CW 14, p. 530, ¶741)

See also: shadow; depression; unconscious; individuation; night-sea-journey; neurosis; loss-of-soul.

References

Jung, C. G. (1970). Mysterium coniunctionis [The conjunction]. In H. Read, M. Fordham, G. Adler, & W. McGuire (Eds.), The collected works of C. G. Jung (R. F. C. Hull, Trans.) (2nd ed., Vol. 14, p. 530, ¶741). Princeton University Press. (Original work published 1955–1956)

Samuels, A., Shorter, B., & Plaut, F. (1986). A critical dictionary of Jungian analysis. Routledge.

Sharp, D. (1991). Jung lexicon: A primer of terms & concepts. Inner City Books.