The tough mineral most likely to survive extensive chemical weathering and form sand grains on beaches or dunes is quartz (SiO2).

Here's why:

* Chemical Inertness: Quartz is highly resistant to chemical weathering. It doesn't readily react with acids or other chemicals found in the environment.

* Hardness: Quartz has a high hardness rating on the Mohs scale (7), meaning it's resistant to scratching and abrasion. This makes it durable enough to survive the grinding and pounding it experiences during transport.

* Abundance: Quartz is one of the most abundant minerals on Earth, making it a common constituent of rocks and sediments.

While other minerals can survive weathering to some extent, quartz is significantly more resistant and therefore forms the majority of sand grains.