If you were planning to back a pie, what ingredients would you use for the crust? The ingredients used to make the Earth’s crust are complex.

The basic ingredients are known as elements. There are 90 known elements that exist in the Earth’s crust. These elements combine with one another in a number of natural ways, creating molecules known as minerals. There are around 3,700 known minerals found in the Earth’s crust, we dozens of new minerals being discovered each and ever year.

These minerals combine to form crystals in regular and distinct patterns. Sometimes the crystals are obvious to the un-aided eye. In other occasions, it is necessary to use a microscope to observe the crystals.

At the surface of the Earth we generally do not find very much solid rock. The solid rock is covered by several feet of ground up, weathered rock, known as regolith, or dirt. However, in some cases, this solid rock does protrude out of the ground, in what is known as an outcropping.

In order to better understand the some 3,700 different types of known rocks, scientists group them into three groups, based on how they are similar, and how they are igneous rock, sedimentary rock, and metamorphic rock.