Dolomite is an important carbonate mineral with a chemical composition of CaMg(CO₃)₂. It is the primary rock-forming mineral of dolomite. Do you have many questions about dolomite? What are its properties? What are its uses? Where is it primarily distributed? How does it differ from other types? This article will provide a detailed explanation. (Estimated reading time: 20 minutes)
What is Dolomite?
Dolomite is formed when limestone and lime mud come into contact with magnesium-rich groundwater. This contact creates a sedimentary rock known as dolomite or dolostone. If you're unfamiliar with the nature of dolomite, you might mistake it for marble or quartzite. While not as soft and brittle as marble, it's also not as hard and durable as quartzite. Dolomite is an extremely abundant non-metallic mineral and a significant source of calcium and magnesium on Earth. Dolomite is also a sedimentary carbonate rock, primarily dolomite, but often mixed with quartz, feldspar, calcite, and clay minerals. Dolomite has significant industrial value. Processed dolomite blocks, dolomite powder, magnesium alloys, cement, and other products are widely used in construction, steel, glass, ceramics, agriculture, and other fields.
Dolomite characteristics
Chemistry and crystal structure
The ideal chemical formula of dolomite is CaMg(CO₃)₂, theoretically containing 30.41% CaO, 21.86% MgO, and 47.73% CO₂. Its crystal structure is trigonal and calcite-type. Unlike calcite (CaCO₃), where all cation positions are occupied by calcium ions, dolomite's structure is composed of alternating layers of calcium and magnesium ions with layers of CO₃²⁻ ions. This ordered arrangement of cations is a key characteristic that distinguishes dolomite from high-magnesium calcite and also contributes to its lower symmetry than calcite.
| chemical composition | CaMg(CO3)2 - Calcium magnesium carbonate. Iron can replace some of the magnesium. |
| color | The transparent to translucent crystals are usually colorless, white, gray, or pink, but can be red, brown, or even black if they contain iron impurities. Massive dolomite is usually light yellow, gray, or white. |
| cleavage | It undergoes perfect cleavage in three directions, forming rhombohedrons. |
| hardness | 3.5 - 4 (relatively soft) |
| proportion | The iron-rich sample ranged from 2.85 (felt relatively light) to 3 |
| luster | The crystals are glassy to pearly, while the blocks are dull. |
| stripe | White |
| Miscellaneous properties | It will effervesce (bubbles) weakly only when using heated dilute acid, or at room temperature if the dolomite is first crushed to a fine powder to increase its surface area. |
| Associated minerals | Quartz, fluorite, galena, chalcopyrite, pyrite, magnesite, clay, gypsum, barite, feldspar, sphalerite, etc. |
Where is dolomite produced?
Production environment and form
Dolomite is not produced in just one form; it exists in many forms in nature:
- Stratiform formation :The most common and important form. Formations that make up entire mountains or are hundreds or thousands of meters thick are called dolomites .
- As associated minerals :In limestone, dolomite can occur as spots, clumps, or laminae.In marble (metamorphic rock), dolomite is one of the common constituent minerals.
- As cement or veins : In the pores or cracks of rocks, dolomite can crystallize out in the form of cement or veins, filling the voids. This is common in diagenesis or hydrothermal activity.
- Modern special environment:Sabkha environment: hypersaline lagoons and supratidal zones along the Persian Gulf coast and the coast of Texas, USA, where dolomite is formed through evaporative pumping and osmotic reflow mechanisms.
Hypersaline lakes, such as the Dead Sea and Australia's Coorong Lagoon, have modern dolomite deposited on their bottoms.
Geographical distribution
World-famous production areas
- The European Alps: This is where the dolomite was named. French mineralogist Théodore de Théodore first described this unique rock in the region, and both dolomite and dolomite are named after him. The Dolomites in northern Italy are the world's most iconic dolomite landscape, characterized by towering white peaks and steep cliffs. The region is a registered World Heritage Site.
- North America:
- United States: There are large and pure dolomite deposits in Missouri, Wisconsin, Illinois, New York, etc. These deposits are mostly marine deposits of the Paleozoic (especially the Ordovician, Silurian and Devonian).
- Canada: Southern Ontario has a large number of Paleozoic dolomite layers and is an important source of minerals.
- Other regions: Mexico, Spain, Switzerland, Russia, Australia and other places also have large dolomite deposits.
Is dolomite limestone?
Dolomite is not limestone , but they are similar in appearance and have a close geological connection.
Fundamental Difference: Mineral and Chemical Composition
Limestone is a rock whose main mineral component is calcite and whose chemical composition is calcium carbonate (CaCO₃).
Dolomite has two meanings:
- Mineral: refers to a specific mineral whose chemical composition is calcium magnesium carbonate (CaMg(CO₃)₂).
- Rock: When the rock is mainly composed of dolomite minerals, the correct name is dolomite, commonly known as "dolomite ore". In daily life, people often vaguely call it "dolomite".
So the difference between a rock composed primarily of calcite (limestone) and a rock composed primarily of the mineral dolomite (dolomite).
| feature | limestone | Dolomite/Dolomite |
| Main mineral components | Calcite (CaCO₃) | Dolomite (Dolomite, CaMg(CO₃)₂) |
| chemical composition | Calcium carbonate (CaCO₃) | Calcium magnesium carbonate (CaMg(CO₃)₂) |
| Reacts with dilute hydrochloric acid | Violent reaction, violent foaming (at room temperature) | Weak reaction, slow foaming (usually requires heating or powdered form to be noticeable) |
| Mohs hardness | 3 | 3.5 - 4 (slightly harder) |
| Causes | primarily deposited from the skeletons and shells of marine organisms or chemically precipitated directly from seawater | Most of them are formed by the replacement of pre-existing limestone by magnesium-containing fluid during diagenesis. |
| Appearance | Usually white or gray, but may appear in other colors due to impurities | Very similar, often light grayish white, light brown, sometimes with a porcelain-like appearance |
Is dolomite marble?
Dolomite is not marble . They are two completely different types of rock, the core difference between which lies in the process of formation (genesis).
Rock formation
Dolomite is a sedimentary rock. It was originally formed over vast geological time periods from sediments deposited on the seafloor or in lake basins. Its formation (dolomitization) is primarily a chemical replacement process that occurs under relatively low, moderate pressures.
Marble is a metamorphic rock. Its "predecessors" can be limestone or dolomite. When these pre-existing rocks are buried deep underground and subjected to immense heat and pressure, the minerals within them recrystallize and grow, becoming larger and denser, completely changing the structure and appearance of the original rock, forming marble. This process is called metamorphism.
| feature | Dolostone | Marble |
| rock type | sedimentary rocks | metamorphic rocks |
| Main minerals | Dolomite (Dolomite, CaMg(CO₃)₂) | Calcite (CaCO₃) or Dolomite |
| Causes | It is formed by the replacement of limestone or mud with magnesium-containing fluid during diagenesis (dolomization). | It is formed by recrystallization of rocks such as limestone or dolomite under high temperature and high pressure metamorphism. |
| structure | Usually has original sedimentary structures, such as stratification and fossil traces (although often destroyed). | A crystalline structure in which the mineral grains are tightly interlocked, and the original sedimentary structure is usually not visible. |
| Main chemical components | Calcium magnesium carbonate (CaMg(CO₃)₂) | Calcium carbonate (CaCO₃) or calcium magnesium carbonate (CaMg(CO₃)₂) |
| Reacts with dilute hydrochloric acid | The reaction is weak, but the reaction is obvious after powder or heating. | Effervesces violently (if the mineral is calcite); reacts weakly (if the mineral is dolomite). |
the original rock, forming marble. This process is called metamorphism.
Is dolomite harmful?
Dolomite is generally harmless and widely used in our daily lives. However, in its sand-making and powder-grinding forms, it may pose a health risk.
Under normal circumstances: basically harmless and widely used
In stable solid form, for example as:
- Building stone (floors, countertops, exterior walls)
- Decorations (sculptures, ornaments)
- Garden landscaping (gravel, rockery)
- Aggregates for building materials
Dolomite is completely harmless. It is stable, non-volatile, and poses no risk of harm to the human body. Its high hardness and low dust production make it safe for everyday contact.
Potential risk 1: Dust inhalation
This is the biggest and most important health risk of dolomite, which mainly occurs during the mining, crushing, cutting, grinding, carving and other processing processes.
- Dolomite minerals contain crystalline silica. When processing creates fine dust that is inhaled into the lungs, these tiny silica particles can settle in the alveoli.
- Long-term or large-scale inhalation may lead to a serious lung disease - silicosis, which is an irreversible, fibrotic lung disease that causes scar tissue to form in the lungs, leading to severe decline in respiratory function and increasing the risk of tuberculosis and even lung cancer.
- In relevant industrial environments, workers must wear professional dust masks (such as N95 level or above), use wet working methods to reduce dust, and be equipped with effective ventilation and dust removal systems.
| State/Scene | Is it harmful? | illustrate |
| Solid complete form | Basically harmless | As a building material or decoration, it is stable and harmless. |
| Dust during processing | harmful | Inhalation of dust containing crystalline silica can lead to silicosis and requires professional protection. |
| Food-grade supplements | harmless | After strict purification to remove heavy metals, it is safe as a calcium and magnesium supplement. |
| Non-food grade accidental ingestion | harmful | May contain harmful heavy metals that can cause poisoning. |
| Confusion with asbestos | Potentially harmful | If the ore is contaminated with associated asbestos, there is a risk of cancer. |
How to process dolomite?
Before establishing a dolomite processing plant, mineral testing is done to understand the dolomite properties.
Dolomite crushing and screening
Crushing and screening processes are carried out to obtain dolomite lumps, which can be used directly as sand and gravel products in the construction industry, or they can be ground or calcined to obtain other products.
Since dolomite is brittle and hard (harder than limestone), it easily scratches iron, so it needs to be crushed in two stages using a jaw crusher and a cone crusher.
Crushing and screening dolomite
- Primary crushing: After mining, large pieces of dolomite enter the jaw crusher for primary crushing.
- Fine crushing: The dolomite then enters the cone crusher for fine crushing. It is crushed into small-sized dolomite blocks to achieve full dissociation of the useful substances in the ore.
- Screening: Crushed dolomite is screened on a vibrating screen. Qualified material is used directly as aggregate or processed further. Unqualified dolomite is returned to the cone crusher for further crushing.
Dolomite processing equipment used in the crushing process:
| equipment | parameter | Specification |
| jaw crusher | Feed size: ≤1200mm | PE jaw crusher |
| Output particle size: ≤350mm | PEX jaw crusher | |
| Capacity: 1-1,000 tons/hour | ||
| cone crusher | Feed size: ≤560mm | Single-cylinder cone crusher: cheap. |
| Output particle size: ≤40mm | Cone Crusher: The most popular. | |
| Capacity: 1-2,200 tons/hour | Hydraulic cone crusher: the best high-end choice. | |
| Vibrating screen | Feed size: ≤200mm | Circular vibrating screen |
| Number of screen layers: 2-4 | High-frequency vibrating screen |
Grinding/Milling and sorting of dolomite
The grinding process is to obtain the dolomite powder needed by the market, mainly including 200 mesh, 325 mesh, 425 mesh and 800 mesh.
- Grinding: The crushed dolomite is transported from the bottom to the silo bucket elevator and then sent to the dolomite vertical roller mill, which can generally be a vrm or ball mill & Raymond mill, and then ground using an electromagnetic vibrating feeder.
- Classification: After grinding, dolomite powder is classified as follows: Dolomite powder that passes the classifier, such as 250 mesh, can be used to produce glass, ceramics, magnesium fertilizer, etc.; 600 mesh, can be used to produce toothpaste, soap, etc.; unqualified powder will be returned for re-grinding.
- Dust Collection: Fine dolomite powder enters the pulse dust collector and the collected dust is sent to the finished product silo. The system has a dust collection rate of up to 99%, low noise, and is environmentally friendly.
The choice of dolomite grinder is very important because it affects the quality of the powder. TONGLI grinder has unique features.
| Dolomite Milling Machine | parameter | Better than other competitors |
| Raymond Mill | Feed size: ≤30mmOutput particle size: 120-325 meshMaximum capacity: 176 tons/hour | 1. Better performance and 4 times longer service life.2. The screening rate reaches 99%.3. The powder is finer, the texture is uniform and there are fewer impurities.4. The price is cheaper. |
| Ultrafine grinding machine | Feed size: ≤35mmOutput particle size: 60-800 meshMaximum capacity: 40 tons/hour |
Calcined dolomite
Crushed dolomite is used in rotary kilns to produce refractory materials, magnesium alloys, cement, etc. Dolomite can be calcined at 1500℃ to obtain magnesium-calcium raw materials such as dolomite sand, magnesium-calcium sand, magnesium-calcium-iron sand, etc., which can then be made into refractory materials. Dolomite can be calcined to produce magnesium alloys: Dolomite - preheating - calcination - cooling - mixing and grinding - pelletizing - refined magnesium - magnesium alloy.
- Preheating: Dolomite rock is uniformly fed into the preheater and preheated to above 800℃.
- Calcination: Energy-saving rotary kiln is selected to calcine dolomite at 1250°C to produce higher grade calcined dolomite.
- Cooling: The high temperature activated calcined white material passes through a cooler to below 100°C. The air is preheated to above 600°C.
- Mixed grinding: put dolomite, ferrosilicon (within 20mm) and fluorite powder into the vertical roller mill for mixed grinding, with the particle size within 100 mesh, equipped with a dust removal system.
- Gum making: Use a lumping machine. A dust removal system can be added.
- Magnesium extraction: Metallic magnesium is extracted by electrolysis or silicothermal reduction.
- Magnesium alloys: Finally, magnesium alloys are made by heat treatment or other methods.
Dolomite can be made into cement after calcination: One method is to calcine alkali powder and then add magnesium chloride solution or magnesium sulfate solution to make magnesium oxychloride cement with better stability. Another method is to calcine it into caustic dolomite and then process it into magnesium hydroxide cement and magnesium oxide sulfate cement. The key equipment in the calcining process is the rotary kiln. TONGLI rotary kiln has the following unique advantages:
- Higher quality products. The kiln body adopts a three-stage heating method of calcination, sintering and pyrolysis, and the heat is evenly distributed.
- The output is 180-10,000t/h, meeting the production needs of large, medium and small dolomite processing plants.
- Equipped with high-efficiency heat exchangers, dust collectors, sealing systems and other auxiliary devices, it is very environmentally friendly.
Practical Uses of Dolomite Products
1. Use of dolomite in steelmaking
Application of Dolomite in Steelmaking: Dolomite powder can improve the hardness and toughness of steel. It is usually used in four ways: (1) as a flux; (2) to protect the lining of refractory materials; (3) as a refractory raw material; and (4) for the production of refractory bricks.
2. Crushed stone for construction industry
The most common use of dolomite is crushed stone. After being crushed and graded, white dolomite can be used as road base material, sand and gravel aggregate in concrete and asphalt, railway ballast, riprap or filler.
3. Magnesium-containing cement
Dolomite cement is a magnesium-containing cement. Magnesium-containing dolomite cement has the advantages of fast setting and hardening, good compressive resistance, good elasticity, and strong wear resistance. It is used in floor tiles, rapid-setting pavement paving, and road crack repair.
4. Magnesium smelting
Application of Dolomite in Magnesium Smelting: Dolomite with a particle size of 30 to 120 mm is smelted by electrolysis and silicothermic reaction. The electrolysis process is complex and difficult to achieve economic benefits, so it is not suitable for small magnesium plants. The silicothermic reaction is to mix the calcined dolomite with ferrosilicon and fluorite into balls, heat them to 1100℃ in a vacuum furnace, and then cool the magnesium vapor to cast it into magnesium ingots.
5. Dolomite fertilizer
Dolomite fertilizer: Dolomite can be used for gardening or crops because the magnesium in dolomite can be used as a magnesium fertilizer to replenish the loss of magnesium in the soil and help tomatoes, onions, beans and other plants grow better.
6. Adjust soil pH
Dolomite soil conditioner can adjust the soil pH value of plants and help plants grow better. Dolomite soil conditioner can regulate soil pH for plants, addressing issues such as slow growth, low maturity, and plant death caused by urea fertilizers. It can also increase crop yields by 15-40%. You can use dolomite for crops that require neutral or alkaline soils, such as cloves, asparagus, and beets.
7. Livestock and poultry feed
Dolomite powder can be added to livestock and poultry feed.
Calcium and magnesium are essential nutrients for animals. Adding dolomite powder to livestock and poultry feed can help animals increase their intake of calcium and magnesium, which is very beneficial for promoting animal growth and reducing diseases.
8. Glass products
Application of dolomite in glass products: Dolomite and limestone are the third-largest glass component, after silica sand and soda ash. Soda ash is the most expensive, while the magnesium oxide in dolomite can reduce costs. Dolomite powder acts as a flux, slowing glass aging, increasing its strength, and improving the plasticity of colored glass.
9. Ceramic products
Uses of dolomite in ceramics: Dolomite powder is the raw material for ceramic bodies and glazes. MgO and CaCO3 can replace talc and calcite, reduce the firing temperature of the body, increase transparency, and dolomite glaze is not easy to smoke and rarely crystallizes.
10. Rubber products
Application of dolomite in rubber products: General calcium magnesium powder for rubber containing dolomite is a new type of additive and colorant that can replace light calcium powder. It has low cost, can prevent crack propagation, and improve reinforcement performance.
11. Water treatment
Application of Dolomite in Water Treatment: Calcined dolomite has the advantages of low cost and no secondary pollution when used in water treatment. Under optimal conditions, it can remove more than 90% of boron in wastewater, meeting drinking water standards, and can also remove metal ions (iron, manganese, etc.) in industrial wastewater.
Conclusion
Although dolomite has certain risks, its economic value is greater. Whether it is crushed dolomite blocks, ground dolomite powder or dolomite sand, it can replace limestone in the production of building materials, cement, fertilizers, glass, ceramics, etc.Dolomite is a mineral with both significant economic value and profound scientific implications. Overall, dolomite is a versatile and versatile material that plays a vital role in a wide range of industries worldwide. Its unique chemical and physical properties, combined with its global distribution, make it an indispensable resource. While the mining and use of dolomite have environmental impacts, the implementation of sustainable practices and its potential to mitigate climate change mark dolomite as a material of considerable interest in the future. It is more than just a rock—it is the cornerstone of modern industry and could be a crucial component in addressing the climate crisis. The formation of dolomite is complex, forming not only through simple magnesium additions in the ocean but also through the evaporation and burial of magnesium-containing water reacting with limestone. Different types of dolomite have unique histories. Baroque dolomite is a special type of dolomite that may be a cement or substitute. It is also known as "white spar" dolomite and has been identified as pearl spar in mineral accumulations. The criteria for selecting models are not as clear-cut as might be expected, and many are subject to diverse interpretations. It is anticipated that a significant amount of research and study on dolomite, its formation, and dolomitization processes will be completed in the future. So thank you for reading today, and in the end we TONGLI Heavy Machinery is an expert in dolomite/coal grinding vertical roller mill and dolomite grinding solution provider.
