i read a few other pages on this forum, and the notion that oil and grapefruit combine to make solid stones is so completely wacky
Many of these pseudostones are from a simple saponification reaction that is taught in first year chemistry. So the reaction is very well known.
Sterol-cholesterol binding is also a well known chemical reaction. In fact sterols are frequently used to lower cholesterol for this reason.
And finally, in cases where people actually had these blobs analyzed the lab determined their chemistry was not of real gallstones but rather saponified olive oil.