Sandstone

Sandstone is compressed and cemented sand. Each grain is typically a tiny quartz crystal that was eroded from older rocks, transported by rivers or wind, deposited in layers, and eventually lithified (turned to stone) by mineral cements filling the spaces between grains.

The colors tell the story of the environment: red sandstone (iron oxide cement, deposited in arid conditions), white sandstone (pure quartz, typically beach or dune deposits), and brown sandstone (iron and clay cements). Cross-bedding patterns (angled layers within the rock) record ancient sand dunes and river channels.

Sandstone landscapes are among the most spectacular on Earth. The red rock country of Utah and Arizona, Uluru in Australia, and the rose-red city of Petra in Jordan are all sculpted from sandstone. These formations were shaped by millions of years of water and wind erosion acting on horizontal rock layers.

Sandstone is identified by its gritty texture (you can feel individual sand grains), visible layering or cross-bedding, and warm colors. It breaks around grains rather than through them, leaving a rough, granular fracture surface.

Distinguish from quartzite (breaks through grains, much harder), limestone (effervesces in acid), and shale (much finer-grained, clay-based).