Cracks

I have done a little woodturning the past few days. I was successful in making a bowl out of purpleheart for my girlfriend but since that I have tried two more times and failed due to cracks in the turning blanks. This is a bit disheartening. One of the blocks was mango that my father brought me from the Philippines and the other was a piece of Olive that I cut myself when a friend was cutting down an olive tree in his yard. I hope that some of the other olive blanks are actually usable but I fear that they are all too cracked to use.