What is it?It is a naturally occurring mineral CaMg(CO3)2.
Dolomite structure is formed by an ionic interaction of Mg2+ (magnesium cation), Ca2+ (calcium cation), and CO32- (carbonate anion). For every two carbonate anions there is one magnesium cation and one calcium cation, thereby making the structure electrically neutral. A common pattern of arrangement of ions is shown below:
- Tactile properties: It is slightly rough and abrasive.
- Visual properties:
- Color: It is often in pink or pinkish and can be colorless, white, yellow, gray or even brown or black when iron is present in the crystal white, grey, pink color
- Lustre: It is vitreous to pearly to dull
- Streak: It is white.
- Diaphaneity: It is opaque
- Structural properties:
- Hardness: 3.5-4 mohs.
- Specific gravity: 2.84-2.86.
- Affinity to water: It has the ability to adsorb and absorb moisture. However, its solubility in pure water is poor though it readily disperses in water.
- Affinity to oil: It has low oil absorption capacity.
- Heat properties:
- Thermal conductivity: 5.1 W m-1 K-1 at 20 °C, It exhibits a two stage decomposition (750 ° Dolomite and MgO; 900 ° CaO and MgO)
- Specific heat capacity: 900 J kg-1 K-1 at 20 °C
- Mean thermal expansion coefficient: 4.1×10-6/°C.
- Melting Point: 2570 °C.
- Electric properties: It is poor conductor of electricity.
- Combustion properties: It is non explosive and non-inflammable.
- Chemical properties: It’s effervesces is weak with warm acid or when first powdered, with cold HCl.
Theoretically, dolomite contains 54.35% CaCO3 and 45.65% MgCO3. Its composition can also be expressed in terms of the oxides. Thus, in other words, it contains 30.4% CaO, 21.7% MgO and 47.9% CO2.However, in nature considerable variations arise in dolomite due to the following factors:
- Varying proportions of lime and magnesia.
- Presence of impurities, chiefly silica, alumina and iron oxide.
- Differences in geological formations.
We have described below the different grades of Dolomite which Anand Talc can provide based on its various applications: