The Present Scenario About Dolomite

Dolomite at present time, does not form on the surface of the earth; yet massive layers of dolomite can be found in ancient rocks. That is quite a problem for sedimentologists who see sandstones, shales and limestones formed today almost before their eyes.
DOLOMITE is a double carbonate of calium and magnesium, CaCO₃, MgCO₃. The mineral was first identified by Count Dolomien in 1791 and named after its discoverer. 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.

Theoretically, Dolomite Contains

CaCO3	54.35%
MgCO3	45.65%

In Other Words, Dolomite Contains

CaO	30.4%
MgO	21.7%
CO2	47.9%

In nature, considerable variations in the composition of dolomite relating to lime and magnesia percentages are found. When the percentage of CaCO₃ increases by 10% or more over the theoretical composition, the mineral is termed 'calcitic dolomite', 'high-calcium dolomite' or 'lime-dolomite'. With the decrease in percentage of MgCO₃, it is called 'dolomitic limestone'. With the variations of MgCO₃ between 5 to 10%, it is called 'magnesian limestone', and upto 5% MgCO₃ or less it is taken to be limestone for all purposes in trade and commercial parlance.
Dolomite usually contains impurities, chiefly silica, alumina and iron oxide. For commercial purposes, the percentage of combined impurities should not go beyond 7% above which, it becomes unsuitable for industrial use. It is then used only for road ballasts, building stones, flooring chips etc.

Hardness	3.5-4
Associated	include calcite sulfide ore minerals fluorite barite quartz and occasionally with gold
Minerals Chemical/Typical composition	white
Color	often pink or pinkish and can be colorless, white, yellow, gray or even brown or black when iron is present in the crystal
Characteristics	Unlike calcite, effervesces weakly with warm acid or when first powdered with cold HCl
Luster	pearly to vitreous to dull
Field Indicators	typical pink color, crystal habit, hardness, slow reaction to acid, density and luster

Dolomite Packing

All grades of Gilsonite are available in various types of packaging:
1. 1 Ton Jumbo bags
2. 25kg package for powder

Dolomite Physical Characteristics

Dolomite Chemical Analysis

Dolomite Habits

Crystalline - Coarse - Occurs as well-formed coarse sized crystals. Massive - Uniformly indistinguishable crystals forming large masses., Blocky - Rhombohedral - Crystal shape resemb les rhomohedrons.
Associated Minerals include albite, anatase, calcite, chlorite group, fluorapatite, fluorite, galena, gmelinite, marcasite, molybdenite, pyrite, quartz, rutile, siderite and sphalerite
Crystal habits include saddle shaped rhombohedral twins and simple rhombs some with slightly curved faces, also prismatic, massive, granular and rock forming. Streak is white.

The Dolomite Group of Minerals

The Dolomite Group is composed of minerals with an unusual trigonal bar 3 symmetry. The general formula of this group is AB(CO₃)₂, where A can be either calcium, barium and/or strontium and the B can be either iron, magnesium, zinc and/or manganese.
The structure of the Dolomite Group is taken from the Calcite Group structure. The Calcite Group structure is layered with alternating carbonate layers and metal ion layers. The structure of the Dolomite Group minerals is layered in such a way that the A metal ions occupy one layer which is followed by a carbonate layer which is followed by the B metal ion layer followed by another carbonate (CO₃) layer, etc. The layering looks like this: |A|CO₃|B|CO₃|A|CO₃|B|CO₃|A|... This ordered layering of different or nonequivalent ions causes a loss of the two fold rotational axes and mirror planes that are present in the Calcite Group structure. Dolomite's symmetry class is bar 3 whereas the Calcite Group's symmetry class is bar 3 2/m. The loss of symmetry allows only simple crystal forms to be used by the Dolomite Group minerals, mostly rhombohedrons.
Dolomite is a very common mineral and ankerite is much more scarce. The other members are considered rare to very rare. The rarity of the members of this group can be tied to the closeness in radius of the A and B ions. In dolomite the A and B ions are calcium and magnesium which have the largest ionic radius differential of the group (approximately 33%). If the A and B ions are close in radius, then they tend to not segregate as easily into the separate A and B layers, which is required to form this structure and therefore these minerals.

Minerals That Belong to the Dolomite Group

• Ankerite Ca(Fe, Mg, Mn)(CO₃)₂
• Benstonite (Ba, Sr)6(Ca, Mn)6Mg(CO₃)₁₃
• Dolomite CaMg(CO₃)₂
• Huntite CaMg3(CO₃)₄
• Kutnohorite Ca(Mn, Mg, Fe)(CO₃)₂
• Minrecordite CaZn(CO₃)₂
• Norsethite BaMg(CO₃)₂
The borate minerals nordenskoldine and tusionite are isostructural with the Dolomite Group minerals.

Dolomite Industrial Use

A major source of magnesium, particularly for agricultural and pharmaceutical applications.

Dolomite General Use

Dolomite is used for manufacturing certain types of refractory bricks used in steel making. The dolomite is heated to a high temperature to drive off the carbonate as carbon dioxide and the remaining material, a mixture of calcium and magnesium oxides, is blended with carbon and other materials and pressed into blocks for the furnaces. The magnesium and calcium oxides have very high melting points and are an excellent, inexpensive refractory material.
Dolomite is also used as a source of magnesium oxide for making magnesium metal and for chemical uses, such as the common laxative milk-of-magnesia. Dolomitic limestone's and dolomites are mined along with limestone and used for crushed stone and aggregates for manufacture of pavement, concrete for construction and as fill material. Dolomite is also used in some cement, as a source of magnesium. Of course Dolomite is also used as mineral specimens.
Dolomite specimens from the Iran are very popular among mineral collectors and dealers. The clear transparent specimens from Iran are rare and unusual, and are in high demand by Collectors.
Dolomite Rock is used as an ornamental and structural stone, and for extracting certain metals from their ores. It is useful in the chemical industry in the preparation of magnesium salts.

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