There are different types of kidney stones. One is caused by high calcium, and one by a lot of tea. I limit both since reading that.
For the oxalate or tea type, green teas have less of it than black, and herbal have still less, down to undetectable levels. This page has a bit of info about that.
http://blogs.webmd.com/healthy-recip...ey-stones.html
As axiom mentioned, one of the best preventatives is drinking water. I am just beginning to appreciate drinking water.