Arkose is a type of sandstone that contains a significant amount of feldspar (typically at least 25%).

Here's why:

* Sandstone Composition: Sandstone is primarily made up of sand-sized grains of quartz, feldspar, and rock fragments.

* Feldspar Content: Arkose distinguishes itself by having a higher proportion of feldspar compared to other types of sandstone. This feldspar is often derived from the weathering of granite or other igneous rocks.

* Formation: Arkose typically forms in environments where there is rapid erosion of granitic bedrock. The feldspar grains haven't had time to break down completely before being deposited.

Let me know if you have any other questions about rocks!