I wouldn't be certain as I can't see any information myself, but I would have thought the dandelion and marigold would have a fair amount in as dandelions are quite high in calcium?
I think it would be interesting to know, we have been feeding the chamomile or the dandelion every so often, as a bit of a change from their normal hay, and have noticed sometimes their urine can be quite cloudy and chalky- but not gritty.