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What Is Dolomitic Limestone?

Natural limestone is primarily made of calcite and aragonite, but dolomite will form in the stone when the calcium ions are replaced by magnesium ions.
Dolomite contains large amounts of calcium and magnesium, which makes it a good fertilizer.
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  • Written By: C. Ausbrooks
  • Edited By: Bronwyn Harris
  • Last Modified Date: 14 August 2014
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Dolomitic limestone is a type of rock that includes up to 50% dolomite. Normal limestone is primarily made up of calcite and aragonite, but dolomite forms in the stone when the calcium ions in the calcite part are replaced by magnesium ions — this process is called dolomitization. This type of rock was once referred to as magnesian limestone in the United States Geological Survey publications, but is now known as dolostone, dolomite rock, dolomite limestone, or dolomitic limestone. Dolomite is a mineral that contains large amounts of calcium and magnesium, which makes it a good fertilizer for nutrient deficient soil.

In addition to working as a fertilizer, the ground rock is also useful for soils that are too acidic, or have an abnormally low pH level. Adding it for the purpose of raising the soil’s pH level is known as liming. Dolomite stone being sold as liming material typically contains a minimum of 30% magnesium.

It takes approximately 1 pound (0.45 kg) of dolomitic limestone per 20 square feet (1.85 square meters) of soil to raise the pH level. Sandy and well-drained soils may require even less, while clay soils often need more. It may take several weeks before a change in pH is observed, but it should not be over-applied. Too much limestone in the soil can result in it having too much magnesium, which will change the soil structure to its detriment.

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This limestone has also been used in the production of ornamental plant containers to balance the pH of their soil and serve as a nutritional source of magnesium and calcium. Around 5 to 10 pounds (2.27 to 4.54 kg) of the substance is generally added to each cubic yard of growing media, including peat moss and pine bark, and then added to the containers. Application may include pelletized or finely ground stone, although studies show that the ground version is more effective for this purpose.

Dolomitic limestone is occurs naturally and is mined in the same areas as dolomite and limestone individually. The stones that are not used for agricultural purposes are often crushed down and used as filler in the manufacturing of pavement and concrete. This stone is found in many different places, including Indiana and Mississippi in the United States, and many areas of India.

In appearance, this limestone is slightly crystalline and is found in a wide variety of colors and textures. Pure dolomite is white to light pink in color, but limestone that contains it may be any shade from white to dark gray. In most cases, it has a greater variety of texture than other types of limestone, and is greater in strength.

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Charlie89
Post 3

@anon246359 -- You're right, there's dolomitic limestone in the Niagra escarpment -- I wonder if they ever take any dolomite from there when making the fertilizer? It would be kind of cool to think that the dolomite lime I lay down in my garden came from there.

anon246395
Post 2

Isn't there dolomitic limestone under Niagara Falls?

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