Welcome to SRP. Looks like a Dark Blue Escher, they made them in different named colors. Good stone. As the other guys said, chamfer the edges with the lapping whether with a diamond plate or sandpaper. Here is a tutorial on the topic. I find I like to use a 325 DMT D8C for most stones and in the kitchen sink under running water. You'll see it in the tutorial Josh Earl did in the link above.