'Demantoid' definitions:

Definition of 'demantoid'

(from WordNet)
noun
A green andradite used as a gemstone

Definition of 'Demantoid'

From: GCIDE
  • Demantoid \De*man"toid\, n. [G. demant diamond + -oid.] (Min.) A yellow-green, transparent variety of garnet found in the Urals. It is valued as a gem because of its brilliancy of luster, whence the name. [1913 Webster]