BTW I never have a problem removing the stone. Just cut around outside of avocado, twists halves apart, take knife and hit the seed with blade just hard enough to just stick knife in the seed (not far or it will be hard to remove it from the blade) and twist knife gently. The seed twists right out then carefully take it off the blade.
Peeps, I've been doing that for a very long time. I have an avocado tree. Sometimes the knife just does not want to sink into the seed. That's when you have to be REALLY careful.