zaffer

Noun

zaffre (countable and uncountable, plural zaffres)

1. Cobalt oxide obtained by roasting cobalt ore, used as a blue pigment.
   • If Zaffre or Regulus of Cobalt be dissolved in the same manner in spirit of nitre, or aqua fortis, a reddish colour is produced on exposing the paper to heat.1791, Erasmus Darwin, The Economy of Vegetation, J. Johnson, page 49
2. A cobalt blue colour, like that of the pigment.