Dolomite

Classification：Sedimentary Rock

Dolomite is a sedimentary carbonate rock. It is mainly composed of dolomite, often mixed with quartz, feldspar, calcite and clay minerals. Grayish white, crisp, low hardness, easy to scratch off with iron. Dilute hydrochloric acid slowly bubbling or not bubbling, and appearance is very similar to limestone. According to the origin, it can be divided into primary Dolomite, diagenetic Dolomite and epigenetic Dolomite. According to the structure, it can be divided into crystalline Dolomite, residual dissimilated particles Dolomite, clastic Dolomite, microcrystalline Dolomite and so on. Dolomite contains high magnesium and white stone powder after weathering. Stronger than limestone. It can be used as flux and refractory material in metallurgical industry. It can produce calcium magnesium phosphate fertilizer and granular fertilizer in chemical industry. In addition, it is also used for ceramic, Glass Batching and building stone. In addition, Fujian Zhangzhou is famous as the Dolomite scenic spot.

Nature：
Dolomite often mixed with calcite, clay minerals, magnesite, gypsum and other impurities. Generally, ore is fine or medium grain structure, which is stratified, massive, brecciate or gravel. Dolomite belongs to the three square crystal system. The crystals are usually saddle shaped rhombohedron. The aggregate is usually granular or massive. The color is colorless, white or light brown to dark brown. Glass luster. When calcined to 700~900 C, it loses carbon dioxide and becomes a mixture of calcium oxide and Magnesium Oxide. It is called caustic dolomite. When the calcining temperature reaches 1500, the Magnesium Oxide becomes a calcite, the calcium oxide becomes crystalline alpha -CaO, and dolomite is one of the widely distributed minerals in the sedimentary rocks.
Main components
Mainly composed of dolomite (more than 50%), but often mixed with calcite and clay minerals. CaMg (CO) (dolomite), containing CaO 30.41%, MgO 21.86% and CO47.73%, often contains isomorphous mixture of iron and manganese. It belongs to carbonate rock. Its shape is limestone. It is slightly different from limestone by adding blister of hydrochloric acid. The main components are calcium, magnesium and silicon, which are three elements. Dolomite is usually light yellow, yellowish gray, gray white, gray brown and light flesh red, and has grain structure, residual structure, clastic structure or biological structure.

Common categories:
Dolomite: mud crystal dolomite, composed of less than 0.005 millimeter dolomite with homogeneous structure, microstratification, few biological residues, sometimes visible ogre fossils, mostly Dolomite.
(2) micro - fine crystal Dolomite: crystal size is different, crystal shape is quite good, appearance is quite like granulated sugar, field can be known as sugar like Dolomite, often by other types of Dolomite recrystallization.
3. Algal Dolomite: similar to algal limestone, that is, Dolomite of algal fossils. Most of the Dolomite in the Proterozoic and Sinian strata of our country belong to this type and may be the primary Dolomite type.
(4) biotic Dolomite and bioclastic Dolomite: the fossil residues are mostly formed by Dolomite metasomatism of bioclastic limestone.
Internal clastic Dolomite: according to the clastic
The size can be divided into gravel, sand and dust Dolomite. They are usually seen in the general Dolomite layer in the form of interlayer. Formed in the upper part of the shallow sea or above the intertidal zone, the debris is impacted by waves or currents.
The oolitic Dolomite: This is a type of secondary Dolomite, namely the Oolitic Limestone into effect by Dolomite.
Because of the large porosity of Dolomite, it is usually the ideal storage layer for oil or groundwater.

Cause:
Dolomite can be divided into three categories according to the forming conditions:
Native Dolomite: Dolomite deposited in situ is evaporated in a dry hot climate (28 ~ 35 C). High salinity, shallow water (0~3 meters deep on the tidal zone), pH value higher than 8.3 in the salty lagoons or bays, can also be formed in the salty lake and often accompanied by a gypsum salt.
Diagenesis Dolomite: in the process of calcium carbonate precipitation, the dolomite is replaced by dolomite, usually distributed discontinuous, in lime rock formation in the form of lenticular or plaque like, sometimes also layered and extended to a certain distance.
Secondary Dolomite, or epigenetic Dolomite, is distributed widely, and is commonly found in fault structural zones.

Development and utilization:
The main application of Dolomite is dolomite, which is widely used in building materials, ceramics, welding, rubber, papermaking, plastics and other industries. In addition, it has also been applied in agriculture, environmental protection, energy saving, medicine and health care.

The utilization of the metallurgical industry:
Dolomite is mainly used as flux, refractory material and magnesium and magnesium compounds in metallurgical industry.
As a flux for ironmaking and steelmaking, the flux Dolomite can play the role of neutralizing acid slag, improve the basicity of the slag and reduce the activity of FeO in the slag, so as to reduce the erosion of the slag to the lining. Light burned dolomite is mainly used in steelmaking, which can improve the fluidity of steel slag and use it as slag making agent. It can not only prolong the life of the converter, improve the fluidity of the slag, and improve the desulfurization and dephosphorization reaction, but also save a large amount of fluorite. At present, the production of 1t steel in China needs to consume 170kgDolomite. Adding dolomite to iron making can dilute slag, reduce slag melting point, reduce fuel consumption and improve the quality of pig iron.
Used as a refractory Dolomite as an alkaline refractory, mainly used in the lining of the steelmaking furnace and the gyration furnace in the steelmaking, and also used as the base of the alkaline hearth furnace and the material of the furnace slope and the remedial material in the smelting process. When smelting high quality ferromanganese and ferrosilicon, Dolomite is often used as a special burden. In the process of steelmaking and slag making, a suitable amount of light burned dolomite or dolomite is added, which is a new method in recent years to replace a part of the lime, thus inhibiting the dissolution of MgO into the slag. Adding dolomite can promote the early slag, make the slag MgO reach the saturation state, improve the stickiness of the slag, have good adhesion to the lining, and play the role of protecting the lining.

Magnesium and magnesium compounds are extracted from magnesium and magnesium compounds by Dolomite, and their production processes are electrolysis or high-temperature metallurgy. The electrolysis process precipitates magnesium hydroxide from the calcined dolomite and the sea water, and then changes into Magnesium Oxide with the hydrochloric acid reaction. Finally, the dried magnesium chloride is fused with sodium chloride and calcium chloride in the external heating electrolysis pool. In high temperature metallurgy, Dolomite and ferrosilicon are made into pellets. In a small diameter vacuum furnace, it is fused at 1100 C to form calcium silicate slag, while magnesium is turned into steam and reused by condensation. By using the same method, Magnesium Oxide and magnesium hydroxide can be produced. Magnesium Oxide is a good refractory material, and magnesium hydroxide is used to produce a series of other useful magnesium compounds and used for plastic packing. Magnesium carbonate is also produced by Dolomite abroad.
The use of Dolomite in the building materials industry after proper calcination, can be processed into white cloud ash, it has white, strong adhesive force, solidifying force and good fire resistance, insulation performance, suitable for internal and external wall coating. After calcining Dolomite, it can be used as magnesium chloride cement and magnesium sulphide cement. Because of its good compressive strength, anti flexure strength, and good performance of fireproof and moth prevention, it can play a very good waterproof effect after adding other fillers, so it can be used as floor material, and it is cheap. Dolomite powder can be used for fissure treatment, pavement preparation and cement mortar sinter slag. Adding 40%Dolomite into cement can accelerate the hydration speed of cement. Dolomite can also be used as a building material. Besides, Dolomite is used as cement and glass and ceramic ingredients in construction industry, which can increase the strength and luster of glass. It is reported that Dolomite has been made by half calcination abroad, and has made inorganic Magnesium Oxide foam and silicate brick.

Dolomite used in the chemical industry is mainly used for the production of Magnesium Sulfate, light magnesium carbonate and other chemical raw materials.
30% of the dilute sulfuric acid and dolomite are mixed, reacted and concentrated in a certain proportion. The calcium sulfate is precipitated at a temperature rise condition. The cooling crystallization of Magnesium Sulfate solution is obtained, that is, Magnesium Sulfate (MgSO x 7HO).
Mg (OH) was extracted from seawater. When calcined dolomite was used as precipitator, MgO in dolomite was also recovered at the same time, so as to increase production.
Calcination, digestion, carbonization and filtration are used to separate dolomite from heavy magnesia water. After heating, decomposition and filtration, dolomite is made of light magnesium carbonate [xMgCO * yMg (OH) * zHO]. Light magnesium carbonate can be decomposed into light Magnesium Oxide and can be used to produce high purity magnesia.

The use of Agriculture:
Dolomite can be used as a neutralizer for soil acidity, and it can also neutralize the acidity caused by the use of urea, and increase crop yield. Dolomite is used mainly as a neutralizer in acid soil, which can compensate for the loss of calcium and magnesium in the soil due to crop absorption. The application of Dolomite can increase the yield of 15-40%. Agricultural lime calcite stone Baiyun treatment, can be used as pesticides to control pests.

Used as filler:
Dolomite can be used as filler for rubber and paper making. High quality Dolomite powder can be used as a substitute for high TiO2 filler and used as a filler for some products. It can improve the chromaticity, weathering resistance, improve mechanical stability, reduce shrinkage and internal tension, reduce water absorption, oil absorption capacity and crack expansion. These products mainly include adhesives, sealing plastics, Paint, detergent and cosmetics, etc.