It is initially rounded with a blackish-brown scurfy outer surface, but expands into a black, shiny, rubbery button-shaped fruitbody, sometimes retaining a raised rim.   The spore depost is black, and this rubs off onto fingers when it is handled. 

Witches' Butter and Warlock's Butter also form black jelly-like blobs on twigs and branches but have a warty hymenium (fertile surface) and white spore print (so they do not stain the fingers black).

Photograph in habitat, showing inner and outer surfaces; note substrate and associated tree species; note spore colour on fingers when handled

On the dead wood of deciduous trees, especially Oak

It is seen in winter but can persist until March