A: According to BBC, an endoskeleton is a bone structure located in the interior of an animal, and an exoskeleton is a bone structure located on the exterior of an animal. Each type of skeleton has unique advantages and disadvantages in helping the animal survive.
Minerals made of only one element are called NATIVE minerals (i.e., silver, gold, mercury, copper). Minerals composed of compounds are simply referred to as minerals (i.e., quartz, which is made up on silicon and oxygen).
An element is a substance that contains only one type of atom. Scientists can classify minerals into groups on the basis of their chemical makeup. Though there are thousands of different minerals, only about 30 are common in Earth's crust. These 30 minerals make up most rocks in the crust.