Here's why:

* Composition:

* Limestone is primarily composed of calcium carbonate, which is chemically reactive and susceptible to dissolution by acidic rain and groundwater.

* Granite is composed of quartz, feldspar, and mica, which are much more resistant to chemical weathering.

* Physical Properties:

* Limestone is relatively soft and porous, making it more susceptible to physical weathering processes like frost wedging and abrasion.

* Granite is hard and dense, making it more resistant to physical weathering.

In summary: Limestone's composition and physical properties make it more vulnerable to weathering processes, leading to a faster rate of breakdown compared to granite.