Well, malic acid isn't actually an herb, but it has been proven to soften 'stones' and is highly recommended by Andreas Moritz . Between chanca piedra and gold coin grass, it's almost a matter of personal physiology and preference. Personally, I'd use chanca piedra and it's what I recommend to my parents (considering I got my genes from them), but I've heard and read wonderful things about gold coin grass as well.

Best bet is to see what *your* body prefers.