I just cut my first corrundum. It was a lavender sapphire from Sri Lanka. I did it with a 600 Crystallite for roughing.
Then I switched to 3k pandamonium on a zinc plus lap. I use 3k and 8k to cut. These grits are not just a prepolish for me.
I found I did experience pitting with my 3k, especially with heavier pressure. Lighter pressure didn’t result in as much pitting.
My stone was only about 1.2cts when I started so not much wiggle room. I moved to 60k on a diamatrix despite the pitting so I wouldn’t wreck my stone trying to cut the pits out. I used 60k to cut the pits out. It took forever.
In retrospect I should have cut on my 8k Batt lap instead of 3k on zinc. I believe it would have resulted in less pitting.
I still have a few more Sri Lanka sapphires and longido rubies to do. I’ll update as I cut them if you’d like.
Here’s a photo of the lavender sapphire. Bear in mind my picture taking skills are awful.