Limestone vs Dolomite…not your usual search comparison.
Granite, marble, sand…these materials people know.
Few people know very much about limestone, and even fewer have even heard of dolomite.
In the following article, we’ll introduce you to the basics of each stone, then compare the similarities and differences encompassed in these lesser-known materials.
Limestone vs Dolomite: The Facts
What is Limestone?
Limestone is an occurring type of sedimentary carbonate rock found on Earth’s surface.
It is formed when crystals of calcium carbonate precipitate out of water containing dissolved calcium.
Limestone is composed of minerals such as calcite and aragonite.
Limestone consists of 80 percent calcite and Dolomite with more than 50% calcium carbonate.
Did you know limestone formations contain approximately 30% of the world’s petroleum reservoirs?
Limestones can be formed through both biological and non-biological processes.
Limestone is primarily made up of Calcium Carbonate (CaCO3) with minor components of 0.2% Organic matter, 5% Quartz and 10% clay minerals.
The mineral is mainly found in marine, continental, and transitional environments.
Limestone is mined from quarries through surface quarrying or underground mining.
Warm, clear, calm, and shallow marine environments favor the formation of limestone.
It forms in areas around the Indian Ocean, Persian Gulf, Caribbean Sea, Gulf of Mexico, Pacific Ocean islands, and the Indonesian archipelago.
Limestone can be found in various forms, including;
Chalk: It is white and soft limestone. The rock is made up of microscopic remains of planktonic organisms that live in the surface waters of tropical seas. The friable limestone exhibits an excellent texture.
Oolitic limestone: The limestone is formed when calcium carbonate is deposited on the surface of sand grains. It is made up of tiny spheres (ooliths) stuck together by lime mud. The sand-sized grains measure less than 2 mm in diameter.
Coquina limestone: A poorly cemented limestone constitutes sand-sized fragments from coral debris or calcareous shell.
Shelly limestone/ Fossiliferous limestone: It comprises skeletons and shells of invertebrates such as crinoids, mollusks, brachiopods, and gastropods that live in water. They contain abundant fossils.
Travertine Limestone: It is a form of limestone that forms where geothermally heated alkaline water and minerals emerge at the surface.
Crystalline limestone: Marble forms when limestone is subjected to heat and pressure.
Physical Properties Of Limestone
Limestone is a soft rock with a standard white to grey appearance.
Limestones richer in organic matter appear in black. Traces of manganese or iron lead to a yellow-red appearance.
Limestones consist of sand-sized grains with skeletal fragments of coral and foraminifera.
Carbonate grains such as ooids, limeclasts, and peloids are significant in composing the limestone.
It is slightly soluble in rain water.
The density of limestone ranges from 1.5 to 2.7 g/cm3.
Limestones integrate a Mohs hardness of 2 to 4.
Dense limestones have a crushing strength of up to 180 MPa.
The limestones fizz when a drop of dilute hydrochloric acid is placed on them.
Limestone exhibits fine, medium, and coarse textures depending on the environment of formation.
Uses of Limestone
Limestone is well known as a building material
It is used as a white pigment or filler in products such as paints.
Limestone is used as a soil conditioner.
Limestone can be used as a decorative addition to rock gardens
It is used as an aggregate for the basis of roads.
It is an essential component of concrete.
It is used as a chemical feedstock for the manufacturing of lime.
Some people even eat limestone as a dietary supplement.
What is Dolomite?
Dolomite is a sedimentary carbonate rock also known as dolostone.
It is an anhydrous double carbonate mineral formed by the chemical alteration of limestone.
The dolomite rock is composed of calcium magnesium carbonate CaMg(CO3)2.
Dolomite is produced through the dolomitization geological process.
The Dolomite occupies approximately 2% of Earth’s crust.
Dolomite formation occurs under anaerobic conditions.
The mineral occurs in the form of dolomite marble, dolomite carbonatite, and dolomite-rich veins.
Magnesium in Dolomite can be substituted by other cations like ferrous iron, lead, barium, zinc, and manganese.
Dolomites occur in different forms of carbonate rock texture, including;
Allochems: Discrete silt to coarser carbonate sand grains, e.g. ooids, pellets, carbonate clasts, and skeletal grains.
Micrite/Microcrystalline: Mud-sized interstitial calcium carbonate matrix
Interlocking: 0.02 – 0.1 millimetre diameter crystals of interstitial calcium carbonate
Physical Properties of Dolomite
Dolomite is poorly soluble in dilute Hydrochloric acid.
On the Mohs scale, the dolomite hardness ranges from 3.5 to 4.
The dolomites are brittle in nature.
The mineral integrates a trigonal crystal system with either a granular, columnar, tabular, massive, or curved face shape, depending on the formation.
Dolomite can be slightly dissolved in acidic water.
It is soft in nature with white, grey, pink, reddish-white, or tan crystals.
Uses of Dolomite
Dolomite can be used as an ornamental stone.
Dolomite can be used as a source of magnesium oxide.
Dolomite is a highly valued industrial mineral that can be collected by museums when large and transparent crystals are formed.
In horticulture, Dolomite is added to soils to buffer PH levels and boost magnesium content.
Dolomite is used in the Pidgeon process for the production of magnesium.
Manufacturing factories can use it in the production of floating glass.
The Dolomite contains minor quantities of radioactive materials; hence it can be used to insulate they from extraterrestrial rays.
In saltwater aquariums, the Dolomite is used as a substrate to buffer changes in the PH of the water.
It can be used as a catalyst for the destruction of tar by biomass gasification at high temperatures.
Similarities between Limestone and the Dolomite
Limestone and Dolomite are closely related sedimentary carbonate rocks. They both comprise calcite minerals.
When subjected to heat and pressure, both limestone and Dolomite begin to recrystallize as the temperature rises.
Limestone and Dolomite incorporate basic chemistry.
Thus, they can be easily separated or crushed into the desired size. They are kiln-fired in the manufacture of cement.
The minerals can be used for construction purposes. Limestone and Dolomite are common building rocks.
They both originate in the same sedimentary environments of warm and shallow habitats.
They are robust, tough and abundant.
Limestone and Dolomite are used in the manufacturing of desulfinators and neutralizers for cleaning industrial waste.
Differences between Limestone and Dolomite
Dolomite is a type of limestone that contains magnesium crystals.
The Dolomite is slightly more complex than limestone. Limestone has a hardness of 3, while Dolomite has a hardness of 3.5 to 4.
Dolomite smolders more slowly than calcite.
Dolomite effervesces gradually with dilute hydrochloric acid, whereas calcite fizzes vigorously.
Why do people confuse Limestone and Dolomite?
Ultimately, these substances are really similar. Dolomite is a form of limestone.
Naturally this would be confusing.
Collectively, the limestone and dolomite minerals are identified as carbonates.
Limestone and Dolomite share the same color range of white-to grey and white-to-light brown.
Although there is a slight variance in solubility, they are both dissolvable in dilute HCL.
They both constitute approximately the same hardness.
If it is important that you use one or the other of these materials, you’ll have to do out of your way to make sure that you’ve got what you think you do.