What a great quilt! If you had not said that it was old, I would have thought it was a modern quilt. The colors are very "today". I don't know the name of the block either and I'm not sure if I've ever seen one just like it. Hope you will finish the quilt one day and enjoy it! It's a wonderful heirloom.
PS - too bad Mom won't let you finish it now so she could enjoy it on her bed for a while....