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Minerals in Bone
"Bones are both strong and light. They are also somewhat flexible." In this demonstration you can see "what makes them strong and how flexible they would be without it. Collagen and minerals work together to make your bones both strong and flexible."
Test a clean and dry chicken bone to see how difficult it is to bend. Be careful, though, you don't want to break it! Now put the bone in vinegar, covering it fully. Keep the bone in the vinegar for about a week. You can test it's flexibility each day but if you do, put it back into the vinegar when you are finished testing it. Is it getting more flexible?
The vinegar dissolves the minerals in the bone, leaving primarily just the collagen, which is what makes bones flexible.
source: Exploring Creation with General Science, Jay Wile