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http://www.itmonline.org/arts/gallstones.htm
*** Gallstones are primarily comprised of cholesterol and calcium, as calcium bilirubinate or calcium palmitate.
Depending on the precise composition, the stones may be soft (more cholesterol) or relatively hard (more calcium).
>>>There may be a large number of small sticky stones, or just one large hard stone, as well as many intermediate conditions, such as a few medium size firm stones (see Figure 3).