"the opus, the great alchemical work"

Alchemy is a continuing theme in Borderlands.  Here Anzaldúa refers to the ultimate alchemical goal of transformation, which is achieved through the opus or "great work."  Although there are many different approaches to understanding and practicing alchemy, one of the most typical descriptions divides the alchemical work into four stages: 

   Nigredo or putrefaction is the stage of blackening: corruption and dissolution

   Albedo or whitening is the stage of purification: burning away impurities (associated with the Moon and the female principle)

   Citrinitas or yellowing is the stage of spiritualisation:  reaching enlightenment   (associated with the Sun and the male principle)

   Rubedo or reddening is the stage of unification:  the union of opposites (male and female, material and immaterial, human and divine)

The movement from black to red has obvious echoes with the Aztec symbolism of "red and black ink."  This image from an early alchemical manuscript shows the work progressing as a key symbol--the dragon--appears in the alchemist's vessel.