Dolomite
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Iran Dolomite

Carbonate minerals are the major constituents of sedimentary rocks; however, they are also found in igneous and metamorphic rocks, either as primary or as secondary minerals. In carbonate rocks formed either by chemical or mechanical deposition, these minerals constitute the main rock-forming components. Sometimes they are also found in great abundance in pelitic, psammitic and psephitic rocks. The principal uses of industrial dolomite, firstly as a refractory and later as a flux, have been linked with iron and steelmaking since the later part of the 19th century. For this reason, industrial dolomite has been regarded as a vital raw material for the iron and steel industry. The other major markets for dolomite are in glassmaking and for agricultural use. Raw dolomite and calcined dolomite have a number of different uses in the iron and steel industry. However, changes in iron and steelmaking technology during the 20th century have had marked effect on the demand for dolomite for specific uses and the market continues to evolve.

What is Dolomite?

Dolomite is a complex mineral. It can participate directly from solutions containing magnesium, calcium and carbonate ions to form cement or unlithified sediment. Most Dolomite forms through the chemical alteration of precursor carbonate rock or sediment-primarily limestone or calcareous muds. These carbonates tend to be unstable, composed chiefly of calcite or its more thermodynamically unstable polymorph, aragonite. When these precursor materials are exposed to magnesium-rich fluids, a portion of the calcium ions to form a more stable magnesium calcium carbonate known as Dolomite.

dolomite exporter

Fig 1. Solid-solution series, in its purest state, Dolomite falls along the calcite-magnesite line in the solid solution-series of calcite, magnesite and siderite. Although the composition of Dolomite is written as [CA Mg(CO3)2], naturally occurring Dolomite ranges from about Ca1.16Mg0.84(CO3)2 to about Ca0.96Mg1.04(CO3)2

Recrystallization can be beneficial to reservoir formation when it generates intercrystalline porosity, but porosity gains can later be negated by the precipitation of pore-filling Dolomite cement or by Dolomite crystal growth that forms large interlocking crystals. Because of the morphology of a Dolomite body is controlled by processes that created it, geoscientists usually try to integrate the mode of origin into their exploration strategies. Over time, however, the recrystallization of metastable Dolomite can obliterate all traces of the mineral’s earliest mode of origin, Dolomite recrystallization can hamper exploration efforts.

Table 1. Physical properties of Dolomite

 

Physical properties of Dolomite

cleavage

{1011} Perfect, {1011} Perfect, {1011} Perfect

color

 

White, Gray, Reddish white, Brownish white, Gray

 

density

2.8 - 2.9, Average = 2.84

Diaphaneity

Transparent to translucent

Fracture

Brittle - Conchoidal - Very brittle fracture producing small, conchoidal fragments

Habit

Blocky - Rhombohedral - Crystal shape resembles rhomohedrons.

Crystalline - Coarse - Occurs as well-formed coarse sized crystals.

Massive - Uniformly indistinguishable crystals forming large masses

Hardness

3.5-4 - Copper Penny-Fluorite

Luminescence

Non-fluorescent

Luster

Vitreous (Glassy)

Streak

white

AssociatedMinerals

include calcite, sulfide ore minerals, fluorite, barite, quartz and occasionally with gold

Best Field Indicators

typical pink color, crystal habit, hardness, slow reaction to acid, density and luster

     

 

 

Dolomite Usages

Row Dolomite and calcined Dolomite have a number of different uses in the iron and steel industry. However, changes in iron and steel making technology during the 20th century have had a marked effect on the demand for Dolomite for specific uses and the market continues to evolve.

The principal uses of Dolomite are those that utilize the mineral in the calcined form (dolomitic lime). The most important of these is as a steelmaking slag flux, where the dolomitic lime replaces some of the quicklime (CaO) used in slag production. In addition to increasing slag fluidity, the presence of magnesia also helps to protect, and thus improve the life of, the steel vessel’s refractory linings, which are made of magnesia. The total quantity used has been declining in line with a fall in iron and steel production. Some 260000 tons of calcined Dolomite were used for this purpose in 2004.

Table 2. Physical and chemical requirements for dolomitic limestone according to use

use

Chemical requirement

Physical requirement

refractories

Magnesium oxide (MgO) not less than 18%. Silicon dioxide (SiO2), ferric oxide (Fe2O3), and aluminum oxide (Al2O3) not exceed 1% each, but lower grades sometimes accepted.

 

Agricultural Dolomite

The use is dependent mainly on the calcium and magnesium carbonate content

Other factors being equal, a soft, friable roc is more acceptable because it is cheaper to process.

Lime (Magnesian)

Magnesian oxide (MgO) content should fall between the limits of 10 and 15%, preferably 11 to 12%

Some manufacturers prefer rock that does not decrepitate during calcining

Steel flux (blast furnaces)

Silicon dioxide (SiO2) less than 3%. Magnesium oxide (MgO) from less than 4%to less than 15% at various plants. Phosphorus pentoxide (P2O5) not more than a trace, that is 0.005 to 0.006%

Some manufacturers specify rock that will not decrepitate when it is heated.

glass

Ferric oxide (Fe2O3) not more than 0.05%, preferably not more than 0.02%. calcium carbonate (CaCO3) content should exceed 98% in limestone, or calcium magnesium carbonate content should exceed 98% Dolomite

 

Concrete aggregate, ballast, road metal, road base

Concrete aggregate should be low in alkalies and free of surface organic matter. Opaline silica is highly undesirable in concrete aggregate. Suitability of other aggregates is based chiefly on durability, particularly toughness.

Must be clean, strong, and durable and low o porosity.

Limestone (CaCO3) and Dolomite (Ca, Mg(CO3)2) are basic raw materials having commercial applications in a number of industries. These carbonates are consumed in the mineral industries (e.g. during the production of cement, lime and glass) and also in metallurgy (e.g. iron and steel), agriculture, construction and environmental pollution control (e.g. flue gas desulphurization). Dolomite is also used as a layer within the media bed of a SSF (Slow Sand Filter) to raise the effluent pH and alkalinity to target levels. Another important market for industrial Dolomite is in glassmaking.

 

iran dolomite

Fig 2. Industrial Dolomite supply in 2004

Table3. consumption of Dolomite 2010-11 to 2012-13 (By Industries)

Industry

2010-11 (MT)

2011-12(R) (MT)

2012-13(P) (MT)

All Industries

7290900

6554500

6804700

Alloy steel

53800(6)

53800(6)

53800(6)

Cement

110500(5)

127900(5)

124200(5)

Ceramic

20200(6)

20200(6)

20200(6)

Cosmetic

400(1)

3300(1)

3500(1)

Ferro-alloys

138800(29)

134500(30)

130700(30)

Fertilizer

11900(4)

10500(4)

8900(4)

Foundry

1900(5)

1900(5)

1900(5)

Glass

84400(31)

109900(32)

89200(32)

Iron & steel 1/

5291900(13)

5312900(41)

5411500(42)

Paint

29500(12)

29800(12)

29300(12)

Refractory

213400(3)

213400(3)

375300(4)

Sponge iron

1333500(55)

535700(62)

555500(63)

Others; (Chemical, electrical, electrode and rubber)

 

700(6)

700(8)

700(9)

Dolomite occurrence

Dolomite occurs in metamorphic rocks chiefly in contact or regionally metamorphosed with Magnesian or dolomitic limestone where it may recrystallize to form a dolomitic marble. At a higher extent of metamorphism, the Dolomite may break down in two stages. Dolomite is different from limestone and may contain minimum 45% of MgCO3. Dolomite has either coarse, granular or fine-grained compact mass.

Dolomite is found in a wide range of settings including hydrothermal veins, lakes, shallow oceans, lagoons and evaporation basins. Theories surrounding the origins of Dolomite continue to evolve. Amid controversy and speculation, many modes of origin have been proposed over the years, and nearly as many have been discarded.

 Future outlook

Over 95% of the total production of dolomite finds outlet mainly in iron and steel and allied industries. The importance of high purity dead-burnt dolomite bricks for lining LD furnaces has gained ground due to LD process of steel making. At the same time, a few of the steel plants have dispensed with the use of dolomite pin blast furnace. Mini-steel plants generally require dolomite for fettling and refractory purposes only.

The resources of the refractory grade dolomite in the country are meagre and this type of material is in short supply but very much required for making tar-bonded dolomite bricks. Therefore, intensive search is needed in non- Himalayan regions for locating deposits of massive non-crystalline dolomite, containing less than 2.5% R O for use in tar-dolomite bricks required for lining of LD steel furnaces. The Sub- Group - II of the Working Group on Minerals for the 12th Plan has recommended the exploration of low silica dolomite in the states of Andhra Pradesh and Odisha which may be initiated by the State DGMs. The Sub-Group has estimated the apparent domestic demand of dolomite at 6.15 million tons by 2011-12 and at 9.46 million tons by 2016-17 at 9% growth rate. 

Table4. Consumption of Dolomite (By Countries)

 

Country

2011-12

2012-13

Qty(t)

Value(USD)

Qty(t)

Value(USD)

All Countries

23270.40108

29343.85094

27143.85163

36907.92467

UAE

13367.61681

14800.20233

16628.18414

20240.16296

Thailand

7088.64669

8585.443611

7236.376691

9619.509834

Philippines

1924.00704

2321.986379

1997.704215

2630.113538

Italy

110.560356

2701.592501

100.7097435

2621.605527

Brazil

-

-

711.5936535

856.229832

 

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