According Catholic theology, what does the suffering of hell consist of? According to Catholic theology, what does the suffering of hell consist of?

If there a principal suffering, what is it?
Catechism of the Catholic Church

IV. Hell


  1034 Jesus often speaks of "Gehenna" of "the unquenchable fire"
  reserved for those who to the end of their lives refuse to believe and
  be converted, where both soul and body can be lost. Jesus solemnly
  proclaims that he "will send his angels, and they will gather . . .
  all evil doers, and throw them into the furnace of fire," and that
  he will pronounce the condemnation: "Depart from me, you cursed, into
  the eternal fire!"
  
  1035 The teaching of the Church affirms the existence of hell and its
  eternity. Immediately after death the souls of those who die in a
  state of mortal sin descend into hell, where they suffer the
  punishments of hell, "eternal fire." The chief punishment of hell
  is eternal separation from God, in whom alone man can possess the life
  and happiness for which he was created and for which he longs.


The emphasis in this passage is mine. The catechism says that separation from God is the chief punishment in hell. The reference to hell fire is placed in a strange context, given that the Church can hardly deny Jesus' words, yet it seems (to me) as if the Church would rather gloss over the hell fire aspect - perhaps because the concept of fire causing suffering to a pure spirit is not something easy to explain.