Here's why:

* Formation Time: Rocks form over incredibly long periods, often millions or billions of years. The geological processes that create rocks (like weathering, erosion, sedimentation, and volcanic activity) happen at very slow rates.

* Limited Supply: While Earth has a vast amount of rock, it's still a finite resource. We are consuming rocks faster than they are being replenished.

* Non-Replenishable: Once a rock is used, it's not easily replaced. Unlike something like wood (which is renewable because trees grow back), rocks are formed through very slow geological processes that we cannot control or speed up.

Examples:

* Fossil Fuels: Fossil fuels (coal, oil, and natural gas) are formed from the remains of ancient organisms over millions of years. They are a non-renewable resource because they are being depleted faster than they are formed.

* Minerals: Minerals are also found in rocks and are essential for many industries. While some minerals are recycled, many are extracted from the Earth and are not readily replaced.

Key Takeaway: While some materials derived from rocks, like sand and gravel, can be recycled or used sustainably, the rocks themselves are not renewable resources.