Brownstone

Brownstone is a brown Triassic–Jurassic sandstone that was historically a popular building material. The term is also used in the United States and Canada to refer to a townhouse clad in this or any other aesthetically similar material.

Brownstone was a popular building material because it is unusually easy to quarry and carve; these qualities also make structures clad in it susceptible to weathering and damage over time. Provided by Wikipedia