Dolomite

MINERAL : DOLOMITE

Dolomite is a double carbonate of calium and magnesium, CaCO3, MgCO3. It is descibed by the French mineralogist and geologist, D. de Dolomieu in 1791 and named after him. They are originally deposited as calcite/aragonite rich limestones, but during a process call diagenesis the calcite and aragonite is altered to dolomite. It is of sedimentary origin and is supposed to have been formed due to chemical action of sea-water containing high percentage of magnesia, on limestone. Since dolomite contains calcium and magnesium it is termed as calcitic dolomite if percentage of CaCO3 is 10% than the normal composition. And it is termed as dolomitic limestone if magnesium is 5 to 10% less.

OCCURENCES AND GEOLOGICAL DEPOSITS

Dolomite is a common sedimentary rock-forming mineral that can be found in massive beds several hundred feet thick. At high temperatures the formation of calcium and magnesium speeds up and places themselves in order in reasonable amount of time. Dolomite crystals also occur in deep-sea sediments, where organic matter content is high. This dolomite is termed organogenic dolomite. Dolomite in addition to the sedimentary beds is also found in metamorphic marbles, hydrothermal veins and replacement deposits. Dolomite forms rhombohedrons as its typical crystal habit. The luster of dolomite is unique as well and is probably the best illustration of a pearly luster. The pearl-like effect is best seen on the curved crystals as sheen of light can sweep across the curved surface.
In India dolomite deposits are available abundantly especially in Madhya Pradesh, Orissa, Karnataka, Gujarat, Rajasthan, Andhra Pradesh, and Maharashtra. In Andhra Pradesh dolomite is deposited in districts like Khammam, Warangal. Raialo in Rajasthan, districts like Tumkur, Shimoga, Chikmaglur in Karnataka, and Bilaspur, Durg, and Jabalpur in Madhya Pradesh from these places dolomite is transported to the glass and steel industries.

PROPERTIES

· The color of dolomite may be pinkish, gray, yellow and sometimes colorless.
· Its crystal system is trigonal.
· Crystal habit is prismatic, granular, columnar, and massive.
· Its fracture is brittle andconchoidal.
· Its crystals are from transparent to translucent.
· Cleavage is perfect in three directions forming rhombohedrons.
· Luster is vitreous and Pearly.
· Streak is white.
· Hardness is between 3.5 and 4.
· Specific gravity is 2.86g/cm3.  

APPLICATIONS/USES

1.Dolomite is mainly used as the fluxing material in blast furnace operation in secondary steel and ferromanganese manufacture.

2.Also used as the refractory, concrete aggregate, ornamental stone, ramming,fettling material in steel melting shop and Pidgeon process for the production of magnesium

3.Processed dolomite in large quantities is used in the production of float glass.

4.Dolomite has become a useful source for the production of magnesite by reacting calcined dolomite with sea-water

5.Dolomite is used as the refractory bricks after calcining and dead burning.

QUESTION AND ANSWERS

1. What is the chemical formula of dolomite?
Ans : Dolomite is represewnted by the chemical formula Ca.Mg(CO3)2.

2. Who described the dolomite mineral?
Ans : Dolomite is descibed by the French mineralogist and geologist, D. de Dolomieu in 1791.

3. What is the luster of dolomite?
Ans : Luster of dolomite is vitreous and Pearly.

4. Crystal habit of dolomite is?
Ans : Prismatic, granular, columnar, and massive.

5. Mention some important applications of dolomite?
Ans : a) Dolomite is mainly used as the fluxing material in blast furnace operation in secondary steel and ferromanganese manufacture.
b) Processed dolomite in large quantities is used in the production of float glass.      

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