There's no single name for a light brown rock! The color brown is caused by a variety of minerals and can be found in many different types of rocks.

To give you a more helpful answer, I need more information. Tell me:

* What kind of rock is it? Is it igneous, sedimentary, or metamorphic?

* What is its texture? Is it coarse-grained, fine-grained, smooth, or rough?

* Where did you find it? Knowing the location can help narrow down the possibilities.

Once I have more details, I can help you identify your light brown rock.