I have been recrystallizing a black marble floor for several months and am noticing that the white veins are starting to raise up from the marble. Some of the veins appear brittle. What is happening?

This is a common problem with black marbles. How often are you using the recrystallization process? I have seen this problem when recrystallization is over applied and performed too often. At this point the floor may need to be re-honed.

An alternative method may be to alternate between recrystallization and powder polishing. For example, if you are polishing the floor once per week you may want to powder polish one week and then recrystallize the next week. The raised veins can be repaired by honing the floor.