What is a mezuzah made of?

There are two parts of the Mezuzah, The Mezuzah Scroll itself and the Mezuzah Case.

The Mezuzah Scroll is made with ink on the parchment of a Kosher animal.

The case can be made of almost any material as its' purpose is to protect the scroll.

Most common materials for the mezuzah case is Metal, stone, wood and glass. I attached a link with showing mezuzah cases in different materials.