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).
MINERALS. Rocks are made of natural, nonliving chemical substances called minerals. Some rocks contain only one mineral. For example, marble is made of the white mineral calcite. Most rocks, however, contain CRYSTALS of several different minerals.