This has been discussed a few hundred times here. The theory that the passed stones are just "olive oil globs' has been disproved so often and so thoroughly that it's a smelly old hat. Interesting that someone of Weil's stature is somehow unaware of that....
Anywhich, check the +/- 60 or so links off the main Liver Flush information page. Many of those links are to threads that discuss this whole issue in great detail and better than I ever could.