Sandstone is a sedimentary rock composed of mostly quartz compressed and cemented together. The cementing agents are the materials that hold the sandstone together. The composition of the stone and the cementing agent used will determine the strength, durability and weather-resistant properties of the sandstone.
Silica cement, also called quartz cement, creates the strongest and most durable type of sandstone used for building. The cement is a result of the quartz grains overgrowing and expanding the crystallized forms until it runs into another quartz crystal. This type of sandstone typically forms in environments that have high-energy currents, such as beaches, marine bars and desert dunes.
Calcite cement is the most common type of cement found in sandstone. The calcite cement typically forms in patches and does not fill all the gaps within the stone. This makes calcite cement sandstone very porous. Calcite is also soluble in wate, which can erode away the cement making the stone even more porous.
Another common cementing agent in sandstone is iron oxide, also called hematite cement. The iron present in the cement will give the sandstone a distinctive red color. According to the Stone Care Techniques website, iron oxide cemented sandstone weather well in dry climates and become harder and stronger, resisting weathering and deterioration.
Other Cementing Agents
Sandstone also has other cementing agents that occur in less common forms. These cementing agents include pyrite, barite and gypsum. These cementing agents form crystals between the particles of the stone. These cements produce a much softer type of sandstone with the particles able to be rubbed off the stone with your hand.