* The Source: Sand grains themselves are typically eroded fragments of existing rocks, such as granite, basalt, or even older sandstone.
* The Process: Over time, these sand grains are transported by wind, water, or glaciers. As they travel, they become rounded and smoothed.
* Cementation: When the sand grains eventually settle in a basin or other low-lying area, they become buried under layers of sediment. Over millions of years, the weight of the overlying sediment compresses the sand grains together. Dissolved minerals in groundwater then act as a natural cement, binding the grains together to form solid rock.
* Types of Cement: The type of mineral that acts as the cement determines the color and properties of the sandstone. Common cementing materials include silica (quartz), calcite, iron oxide, and clay.
So, in simple terms, sandstone is essentially sand that has been compressed and cemented together over long periods.
