Final answer:
Window glass is the material that is made mostly of the mineral quartz, also known as silicon dioxide (SiO₂).
Step-by-step explanation:
The material made mostly of the mineral quartz is window glass. Quartz is one of the most common minerals in the Earth's crust and is also known as silicon dioxide (SiO₂).
In its amorphous form, silicon dioxide is known as “fused silica”, which is the most common component in glass production. This substance, when heated, becomes transparent and forms the base of various types of glass, including window glass. Small pieces of colored glass can be assembled to create stained-glass windows, a technique used for over a thousand years in sacred buildings.