Small irregular cups with a short stem and a turquoise or blue-green felty outer side and darker, smooth blue-green inner side.  The fungus stains the rotten wood substrate a verdigris or blue-green colour.    Chlorociboria aeruginascens and Chlorociboria aeruginosa both produce similar cups and staining of the substrate. 

C aeruginosa is described in some sources as having a whitish hymenium and more regular shape, but in others it is described as being macroscopically nearly identical to C aeruginascens.  To be on the safe side, microscopic examination of spores is needed.

Photograph the cups and/or the stained wood; note substrate and habitat

On rotten wood of deciduous trees, often oak.

Widespread and fairly frequent in Britain.