Limestone vs Sandstone
Limestone and sandstone are found in large amounts around the world, and they are very common sedimentary rocks. However, their origin, composition and other properties of these two are different, making them unique.
Limestone is commonly found in marine environments, and they are classified as sedimentary rocks. These are mainly formed in shallow, warm and calm waters. Biological activity also plays an important role in forming limestone. Normally, they are formed in waters where carbon dioxide concentration is low so that the sedimentation is quite easy. Marine water receives calcium from land. There is a lot of calcium carbonate containing materials, such as shells of mollusks and other sea animals, coral, skeletal structures of sea animals, etc. When these are accumulated in the form of calcite (other waste materials also tend to incorporate into this when accumulating), they are known as limestone. They are also categorized as biological sedimentary rocks. There is another type of limestone known as chemical sedimentary rocks. They are formed by direct precipitation of calcium carbonate in sea water. However, the biological sedimentary rocks are more abundant than chemical sedimentary rocks. In pure limestone, only calcite is there, but often they can contain impurities by mixing other materials like sand. So, limestone can be defined as a sedimentary rock, containing more than 50% of calcium carbonate in the form of calcite. Other than in oceans and seas, limestone can be formed in lakes or other water bodies with necessary conditions. In the world, limestone formation can be seen in Caribbean Sea, Indian Ocean, Persian Gulf, Gulf of Mexico, around Pacific Ocean islands, etc.
The nature of limestone depends on how it is formed. They can be in massive sizes, crystalline, granular, etc. They are classified into several groups according to their type of formation, composition or appearance. There are many classifications too. Some of the common limestones are chalk, coquina, lithographic limestone, oolitic limestone, fossiliferous limestone, tufa, etc. There are many usages of limestone too. They are commonly used as an ingredient for cement and glass manufacturing, hence an essential construction material. Since, limestone has a basic nature; it is used to neutralize acidic water bodies.
Sandstone is also a widely found sedimentary rock. It is formed in many environments such as oceans, lakes, deserts, etc. They are mostly formed by sand grains; therefore, contain quartz and feldspar in high quantities. Sandstone formation takes place in, Sahara desert in Africa, central Australia, Arabian deserts, western United States, etc. There can be different types of sandstones in various colors. Sandstones are used for cement or glass manufacturing. It has an aesthetic value, as well as an ornamental value. They can be cut, polished and then used as tiles or beautiful rocks for buildings or as monuments.
What is the difference between Limestone and Sandstone?
• Limestone is forming from calcium carbonate sedimentation, whereas sandstone is formed from mineral grains/ sand.
• Limestone can be biological sedimentary rocks; sandstones are not.
• Limestone mostly has calcite. Sandstone mostly has quartz.
• Limestone has a crystalline structure. In sandstone, sometimes the grains can be loosely cemented; therefore, separate grains can be seen.
• Limestone formation is quite restricted to marine or other aquatic environments, whereas sandstone formation happens in many places.