Here's why:

* Abundant: Quartz is one of the most abundant minerals on Earth.

* Hard and Durable: Quartz is a very hard and durable mineral, making it resistant to weathering and erosion.

* Resistant to Chemical Breakdown: Quartz is chemically inert, meaning it doesn't easily react with other substances, making it last a long time.

While quartz is the most common, other minerals like feldspar, mica, and even small amounts of heavy minerals can also be found in sand, depending on the source of the sand.