Spalted Maple is technically not a species of wood.  It is Maple wood that has been allowed to begin the initial stages of decay.  The black or brown lines you see is called spalting.  Spalting offers the wood dark contrasting lines where the fungus has begun to attack the Maple wood.  When Spalted Maple is dyed it offers a real contrast with the wood and spalting lines making it a great wood for pen blanks.