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).
Each rock is made up of one or more different minerals. For example, granite. might be composed of the minerals quartz, orthoclase feldspar, mica, and hornblende. Limestone is an example of a rock that consists of only one kind of mineral: calcite. Although there are 2000 or more kinds of minerals in the earth, only about a dozen.