* Quartz is a very hard and durable mineral made of silicon dioxide (SiO2). It's commonly found in sand, granite, and many other rocks.

* Feldspar is a group of minerals that are rich in aluminum, silicon, oxygen, sodium, potassium, and calcium. It's a major component of many igneous and metamorphic rocks.

Together, quartz and feldspar make up a significant portion of the Earth's crust, and they are essential components of many rocks and soils.