> That served to remind me that the 'medically orthodox' (so to speak) among the posters here have a very clear idea of what consitutes gallstones: they are hard, calcified stones, typically but not invariably black.
As someone who is knowledgeable about orthodox medicine, orthodox medicine fully reocgnizes more than one class of gallstone. Orthodox medicine acknowledges that most Gallstones are *cholesterol* stones (80%). Cholestrol is a soft waxy substance. There are other classes of gallstone too including calcified/pigment gallstones.
Lay people often think that Gallstones only refers to calcified Gallstones (I did too until I investigated the literature) - this is not true. Although calcified gallstones are the ones which cause the most problems and so these are the ones the medically untrained hear about.
Again note the distinction between cholesterol gallstones: "Cholesterol stones are usually white or yellow in color and account for about 80 percent of gallstones. They are made primarily of cholesterol."
and calcified gallstones: "Pigment stones are small, dark stones made of bilirubin and calcium salts that are found in bile. They account for the other 20 percent of gallstones. Risk factors for pigment stones include cirrhosis, biliary tract infections, and hereditary blood cell disorders, such as sickle cell anemia."
To answer your question - it is unlikely that one type of gallstone turns into the other because of their different constituent ingredients. Cholesterol gallstones form in all people (to some extent), whereas pigment/calcified gallstones tend to be associated with some kind of pathology.
PS. I feel this answer deserves an (R) and possibly a newsletter recommendation (N).