Sandstone is a sedimentary rock formed under oceans, lakes and rivers, where sand has been laid down and buried. It is composed of cemented sand grains, rock fragments, minerals and organic material. The cementing material that binds sand grains together and occupies spaces between them is typically silica and calcium carbonate, which are often derived either from dissolution or from alteration of the sand after it was buried. Sandstone colour is usually yellow, red, brown or grey to white reflecting the variation in mineral content and cement.
Sandstone can be softer to harder, depending on clast and cement composition. The more calcium carbonate it contains, the harder and more resistant to weathering it is. Sandstone containing lots of quartz is recognized for its natural strength, durability and slip-resistant properties. Since sandstone beds often form highly visible cliffs and other topographic features, certain colours have been strongly identified with certain regions. Sealing sandstone is highly recommended as stain removal can be limited due to its porosity and texture. One of the best examples of architecture using sandstone is the city of Petra.
Interior and exterior walls