Fomitopsis spraguei
Fomitopsis spraguei made quick work of this oak stump.  This brown rot
fungus degrades cellulose in its search for food, leaving behind lignin.
These two sets of images show a ten day time lapse.  
Summer.
The margin of Fomitopsis spraguei varies in color; reddish brown (usually
when very young) to light brown and will bruise green when handled.  
See Fomitopsis spraguei at
Fungi Growing on Wood
See photo series of Fomitopsis spraguei at
The Mushroom Hunter
Plastic alternative made from lignin
TECNARO