xylindein

from The Century Dictionary.

• noun A blue compound contained in green, decayed wood which has been infected with Peziza æruginosa. It crystallizes in quadratic plates which have a strong coppery luster.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Chem.) A green or blue pigment produced by Peziza in certain kinds of decayed wood, as the beech, oak, birch, etc., and extracted as an amorphous powder resembling indigo.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A quinone pigment, a dimeric naphthoquinone derivative, responsible for the characteristic bluish-green stain of wood infected by the Chlorociboria aeruginascens mushroom.