Dolomitic Limestone

There are various types of rocks found in nature, such as igneous, metamorphic and sedimentary rocks. Their origin or the kind of formation they undergo is the criteria that divides them into these categories. Igneous rocks are formed from the lava or magma of volcanoes. Metamorphic rocks, as the term suggests are igneous or sedimentary rocks that undergo transformation over a span of time.

Sedimentary rocks are formed due to layers or sediments of various materials such as earth and deposits from water bodies. These sedimentary rocks contain many mineral and organic deposits. There have been examples of fossils being found in these rocks. Limestone is a sedimentary rock that mainly consists various forms of calcium carbonate such as calcite or aragonite. Dolomite is also a sedimentary rock that consists mainly of magnesium calcium carbonate salts. Magnesium is the main mineral found in dolomite. Sometimes, limestone gets substituted by dolomite. These rocks are known as dolomitic limestone.

Facts About Dolomitic Limestone
These rocks contains 10 to 50 percent of dolomite and more of calcite which varies from around 50-90 percent. This is a natural process, probably one of the many types of chemical reactions that leads to formation of dolomite within limestone. The exact reason behind this is not very clear. A rock is referred to as dolomitic limestone only when the dolomite percentage is more than 10 percent and less than 50 percent. The United States Geological Survey initially named this rock magnesian limestone, as it contained magnesium. However, now it is also known as dolostone or dolorock.

Decomposition of this rock is a very complex process that is studied in chemistry and to an extent in geology. It requires higher temperatures for decomposition wherein it first forms a salt of calcium carbonate and magnesium oxide and then decomposes to calcium oxide and magnesium oxide. At each stage there is formation of carbon dioxide gas.

Dolomitic Limestone Fertilizer
There are a various uses of limestone that are known to many. But if you are into agriculture or even gardening for that matter then you need to know about dolostone. It is one of the main ingredients of many fertilizers. The purpose behind including this is the presence of macro-nutrients, magnesium and calcium. These are usually present in soils, but when the soil is too acidic and lime is used to adjust the pH, addition of these nutrients is necessary. Thus its fertilizer has it all, lime to maintain the pH at optimum levels, calcium and magnesium. Addition of this rock raises the pH of acidic soils to a preferred range of 6 to 6.5, which is on the higher acidic pH side on the pH scale. The advantage of adding this particular ingredient to fertilizer is that when the pH of the soil is adjusted by the lime, the nutrients become more readily available for absorption. This range is also suitable for microbial growth in soil to convert elemental nitrogen to forms that can be absorbed by the roots. It also improves the texture and quality of soil with respect to aeration and water absorption.

Many a time, dolostone is available in various forms to as an additional ingredient to your fertilizer. Studies have shown that the smaller or powdered form of this is more effective than the coarser particles. Pelletized form is also available in the market which are first crushed into powder as fine as flour and then made into pellets for fertilizers which dissolve due to moisture.

Certain types of limestones have a higher content of calcium. This is known as high calcium limestone. This limestone is used in agriculture but also has an industrial application. High calcium limestone is used as raw material in the precipitated calcium carbonate markets, (PCC) which is used to make good quality paper. It also finds an application in the sugar industry.

The products of these rocks are not that expensive and are therefore extensively used in agriculture.