Many people ask me what bluestone is when im discussing their brick steps or maybe a hearth and mantle. In these pictures the finish you see is called a thermaled finish on the top and edges. A torch is used in conjunction with water to super heat the water, make it expand and pop the layer of stone off the face. Neat eh?
The other way bluestone comes is with a rocked face. Normally it is thermaled like mentioned then a chisel is taken to the edge to rock it. Like seen on this hearth.
When building steps on the outside of your house bluestone is the recommended material for the tops. The stone is larger so there are fewer mortar joints to let moisture inside to cause problems. They are also fairly hard and will last much longer then brick tops.