Hey dirts,
Yes, the moonstone is a tricky but fun stone to work with.
I'm glad I got to check some of Tim's out. I really don't know where known good sources are on the east coast.
Mostly I recall them being further north, so I don't have any idea if any workable material is found in Georgia. Good question.
As far as hardness goes between the moonstone and chrysoprase, there isn't much difference.
moonstone, 6-6.5
chrysoprase, 6.5-7
My rough wheels are 80 and 100, and would use them on either material depending on how much rough I want to remove.
That piece of chrysoprase probably was already full of fractures for it to fall apart that way.
Now the moonstone would be a little different story.
And I'm assuming you were using that 100 grit wheel wet.
Sorry, I can't help you out with your tumbling questions but I don't have one so I don't have much experience with them.
I passed on a nice unit for sale last year and I probably should've gotten it.
Good luck with the grindin'.