Dolomite is a common rock-forming mineral. It is a calcium magnesium carbonate with a chemical composition of CaMg(CO3)2. It is the primary component of the sedimentary rock known as dolostone and the metamorphic rock known as dolomitic marble. Limestone that contains some dolomite is known as dolomitic limestone.
Dolomite is rarely found in modern sedimentary environments but dolostones are very common in the rock record. They can be geographically extensive and hundreds to thousands of feet thick. Most rocks that are rich in dolomite were originally deposited as calcium carbonate muds that were post-depositionally altered by magnesium-rich pore water to form dolomite.
Dolomite has a Mohs hardness of 3 1/2 to 4 and is sometimes found in rhombohedral crystals with curved faces. Dolomite produces a very weak reaction to cold, dilute hydrochloric acid; however, if the acid is warm or if the dolomite is powdered a much stronger acid reaction will be observed. (Powdered dolomite can easily be produced by scratching it on a streak plate.).
Dolomite is very similar to the mineral calcite. Calcite is composed of calcium carbonate (CaCO3) while dolomite is a calcium magnesium carbonate (CaMg(CO3)2). These two minerals are one of the most common pairs to present a mineral identification challenge in the field or classroom. The best way to tell these minerals apart is to consider their hardness and acid reaction. Calcite has a hardness of 3 while dolomite is slightly harder at 3 1/2 to 4. Calcite is also strongly reactive with cold hydrochloric acid, while dolomite will effervesce weakly with cold hydrochloric acid.
Dolomite has an enormous number of uses, like :
- The most common use for dolomite is in the construction industry. It is crushed and sized for use as a road base material, an aggregate in concrete and asphalt, railroad ballast, rip-rap or fill. It is also calcined in the production of cement and cut into blocks of specific size known as "dimension stone".
- Dolomite's reaction with acid also makes it useful. It is used for acid neutralization in the chemical industry, in stream restoration projects and as a soil conditioner.
- Dolomite is used as a source of magnesia (MgO), a feed additive for livestock, a sintering agent and flux in metal processing and as an ingredient in the production of glass, bricks and ceramics.
- Dolomite serves as the host rock for many lead, zinc and copper deposits. These deposits form when hot, acidic hydrothermal solutions move upward from depth through a fracture system that encounters a dolomitic rock unit. These solutions react with the dolomite which causes a drop in pH that triggers the precipitation of metals from solution.
- Dolomite also serves as an oil and gas reservoir rock. During the conversion of calcite to dolomite a volume reduction occurs. This can produce pore spaces in the rock that can be filled with oil or natural gas that migrate in as they are released from other rock units. This makes the dolomite a reservoir rock and a target of oil and gas drilling.
Physical Properties
| Appearance | White Crystalline Powder. |
| Sp. gravity | 2.6 - 2.8 |
| Oil absorption | 12 to 14 |
| Volatile content | Max. 0.5% |
| PH of 10% slurry | 8.5 to 9.0 |
| Coarse Particles | Max. 0.5% |
Chemical Composition
| CaCO3 | 56.5% |
| MgCO3 | 43.0% |
| CaO | 31.5% |
| MgO | 20.5% |
| Fe2O3 | 0.5% |
| SiO2 | 1.5% |
| Al2O3 | 0.5% |
Industrial Applications
Paints
Used widely in cement paints, exterior paints, primers, putties, powder coatings and industrial finishes.Plastic
Used in PVC footwear, PVC pipes, cables and others.Paper
Used as integral filler in paper to give smoothness and gloss.Adhesives
Used in adhesives and carpet backing.Rubber
It is used in toothpaste, cosmetic and soap industry.
Our Suggested Grades
| Grade | Brightness | Particle Size | Top Cut | Oil Absorption | Application |
| DL -05 | 96% | 2 - 5 micron | 20 | 26 | Paints, Plastics |
| DL -10 | 95% | 10 micron | 40 | 24 | Paints, Paper, Plastics |
| DL -30 | 94% | 20 micron | 50 | 22 | Paper, Rubber, Adhesive |