Select the one substance that is not a mineral.

 - Native gold is a solid. It is a pure substance.
 - Chrysotile is a pure substance. It is not made by living things.
 - A turtle shell is not a pure substance. It is formed in nature.
Compare the properties of each substance to the properties of minerals. Select the substance whose properties do not match those of minerals.
Native gold is a mineral.
Chrysotile is a mineral.
A turtle shell is not a pure substance. But all minerals are pure substances.
So, a turtle shell is not a mineral.