Chlorociboria aeruginosa or Chlorociboria aeruginascens

This fungus is also called the Emerald Elf Cup.   The genus includes 23 species. The green staining of wood is more often seen than the cup like fruiting bodies.  It is an Ascomycete.  The hyphae and fruit bodies of all species make xylindein, a secondary metabolite that stains the substrate wood blue-green, with “green oak” being a valued commodity in woodworking.