Natural Sunstone Crystal Heart Carving

Sandstone is a sedimentary rock that forms when sand grains are cemented together over millions of years. The grains are often made of quartz or feldspar minerals that have been worn off other rocks and ground into pebbles. The grains can be deposited in the sea, by rivers, or in deserts. Groundwater then precipitates minerals that cement the grains together. 

Sandstone can contain sand crystals, which are formed when cementing minerals form crystallographically continuous crystals in the cement. These crystals can look like a barite rose, a gypsum rose, or a calcite crystal. If you cut a thin section of a sand crystal, you can see that the cement is optically continuous between the grains. 

Sandstone can also contain other minerals like calcite, clay, or mica. These minerals, along with impurities in the sand grains, can cause sandstone to vary in color. The most common colors are tan, brown, yellow, red, gray, pink, white, and black. Certain colors of sandstone are associated with certain regions, such as the red rock deserts of Arches National Park. 

Sandstone formations are often porous and permeable, meaning they contain small pores that allow fluids to flow through. Drilling into underground sandstone formations can produce water and oil. Sandstone is also commonly used in construction, with examples including Manhattan's brownstones, Washington DC's Smithsonian Institution, and Jordan's ancient Petra.