I'm pretty convinced it's all right - they're liver stones . Liverstone (gallstones?) are made in 90-99% from cholesterol - ofcourse they will float if not weighted down by other fecal matter. Mushy and strange shaped - great explanation in Glowing - it takes time to harden, and even the hardened ones can be softened in preparations (i've had mine preps), just re reda some section of the book i used to flush about the part where you "melt" them, that would make them musshy etc.
I've never red Hulda's book, but you can be damn sure she made sure not to call gallstone something that's not a gallstone! As to the coulour, depends on the composition - i've red somehwer calcium whitens them. And ofcourse some are not from cholesterol (maybe the more "serious" ones). So it's not really nice to freak ot people with wild theroies like that ;-)