cold case rondel

The signs are better set in stone
Than memories that fizz in glass.
First as tragedy, then as farce -
A light laugh cut into a groan.

A single moult of hair, not mown,
Found in among the buds and grass.
The signs are better set in stone
Than memories that fizz in glass.

I broke each tooth but lost a bone.
Send me to the back of the class.
Because of you, sharpeye smartarse,
I'll end my days in dark alone.
The signs are better set in stone
Than memories that fizz in glass.

What is a rondel?