gallstones are usually made up of bits of bile and cholestrol and other digestive juices excreted from your liver that don't move out of the gallbladder correctly and form stones.
Kidney stones are most of the time made up of types of calcuim, but sometimes they are different crystalline substances, salts or oxylates. Kidney stone form when there is an imbalance in fluid levels and the urine in very strong and minerals deposit in the kidney.
Gallstones form after problems with the digestive systems, bile ducts, cholestrol or other incident.
-JL
one bird with the two forementioned stones