The Collaborative International Dictionary of English v.0.48:

Essonite \Es"so*nite\, n. [Named from Gr. ? inferior, because
   not so hard as some minerals it resembles, e. g., hyacinth.]
   (Min.)
   Cinnamon stone, a variety of garnet. See Garnet.
   [1913 Webster]

WordNet (r) 3.0 (2006):

essonite
    n 1: a garnet ranging in color from yellow to brown [syn:
         cinnamon stone, essonite, hessonite]