A common rock-forming mineral and the major constituent that a sedimentary rock known as "dolostone"Article by: Hobart M. King, PhD, RPG

Dolomite crystals: Dolomite crystals from Penfield, brand-new York. This specimen is roughly 3 inches (6.7 centimeters) across.

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Dolomite: A Mineral and a Rock

"Dolomite" is a word that is supplied by geologists in two various ways: 1) as the surname of the mineral dolomite; and, 2) as the name of a rock recognized as dolomite, dolostone, or dolomite rock.

This web page is about the mineral dolomite. If friend are looking for an article about the rock, please go here.


Granular Dolomite: Dolomitic marble native Thornwood, new York. This specimen is approximately 3 inch (6.7 centimeters) across.

What is Dolomite?

Dolomite is a common rock-forming mineral. That is a calcium magnesium carbonate through a chemistry composition that CaMg(CO3)2. That is the main component that the sedimentary rock recognized as dolostone and also the metamorphic rock recognized as dolomitic marble. Limestone that contains some dolomite is well-known as dolomitic limestone.

Dolomite is rarely uncovered in modern-day sedimentary environments, yet dolostones are an extremely common in the absent record. They deserve to be geographically extensive and hundreds to countless feet thick. Most rocks that room rich in dolomite were initially deposited together calcium carbonate muds the were postdepositionally altered by magnesium-rich spicy water to kind dolomite.

Dolomite is likewise a usual mineral in hydrothermal veins. There it is often associated with barite, fluorite, pyrite, chalcopyrite, galena, or sphalerite.In these veins it regularly occurs together rhombohedral crystals i beg your pardon sometimes have actually curved faces.

Physical properties of Dolomite
Chemical Classification Carbonate
Color Colorless, white, pink, green, gray, brown, black
Streak White
Luster Vitreous, pearly
Diaphaneity Transparent come translucent
Cleavage Perfect, rhombohedral, 3 directions
Mohs Hardness 3.5 to 4
Specific Gravity 2.8 to 2.9
Diagnostic Properties Rhombohedral cleavage, powdered type effervesces weakly in dilute HCl, hardness
Chemical Composition CaMg(CO3)2
Crystal System Hexagonal
Uses Construction aggregate, cement manufacture, dimension stone, calcined to develop lime, periodically an oil and gas reservoir, a source of magnesia for the chemical industry, farming soil treatments, metallurgical flux


Dolostone: Dolostone native Lee, Massachusetts. The "sugary" sparkle shown by this absent is led to by light mirroring from small dolomite cleavage faces. This specimen is about 4 inches (10 centimeters) across.

Physical nature of Dolomite

The physics properties of dolomite that are useful for identification are presented in the table top top this page. Dolomite has three directions of perfect cleavage. This might not be noticeable when the dolomite is fine-grained. However, when it is coarsely crystalline the cleavage angles can easily be observed with a hand lens. Dolomite has actually a Mohs hardness that 3 1/2 to 4 and is sometimes found in rhombohedral crystals v curved faces. Dolomite produces a an extremely weak reaction to cold, dilute hydrochloric acid; however, if the mountain is warm or if the dolomite is powdered, a much stronger acid reaction will certainly be observed. (Powdered dolomite can quickly be created by scratching it on a streak plate.)


Dolomite is very similar to the mineral calcite. Calcite is written of calcium carbonate (CaCO3), when dolomite is a calcium magnesium lead carbonate (CaMg(CO3)2). These two minerals are among the most common pairs to existing a mineral identification challenge in the ar or classroom.

The best method to tell these minerals personal is to take into consideration their hardness and acid reaction. Calcite has actually a hardness of 3, when dolomite is contempt harder in ~ 3 1/2 to 4. Calcite is additionally strongly reactive v cold hydrochloric acid, if dolomite will effervesce weakly v cold hydrochloric acid.


Dolomite aggregate: Dolostone, provided for asphalt paving indigenous Penfield, new York. This specimens are roughly 1/2 inch to 1 inch (1.3 centimeters to 2.5 centimeters) across.

Solid Solution and also Substitution

Dolomite occurs in a hard solution series with ankerite (CaFe(CO3)2). When little amounts of iron are present, the dolomite has a yellowish come brownish color. Dolomite and also ankerite room isostructural.

Kutnahorite (CaMn(CO3)2) additionally occurs in solid solution with dolomite. When small amounts that manganese room present, the dolomite will be colored in shades the pink. Kutnahorite and also dolomite room isostructural.


Dolomitic marble from Thornwood, new York. This specimen is around 4 inches (10 centimeters) across.


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Uses that Dolomite

Dolomite together a mineral has actually very few uses. However, dolostone has an enormous number of uses since it occurs in deposits that are large enough to mine.

The most common use because that dolostone is in the building and construction industry. That is crushed and also sized for use as a roadway base material, an accumulation in concrete and asphalt, rail ballast, rip-rap, or fill. The is also calcined in the production of cement and cut right into blocks of certain size well-known as "dimension stone."

Dolomite"s reaction v acid additionally makes it useful. It is supplied for acid neutralization in the chemical industry, in stream restoration projects, and as a soil conditioner.

Dolomite is used as a resource of magnesia (MgO), a feed additive for livestock, a sintering agent and flux in steel processing, and also as one ingredient in the production of glass, bricks, and ceramics.

Dolomite serves together the hold rock for numerous lead, zinc, and also copper deposits. These deposits type when hot, acidic hydrothermal solutions move upward from depth v a fracture device that encounters a dolomitic absent unit. These options react through the dolomite, which reasons a fall in pH the triggers the precipitation of metals from solution.

Dolomite likewise serves together an oil and also gas reservoir rock. Throughout the conversion of calcite to dolomite, a volume reduction occurs. This can create pore spaces in the rock that can be filled v oil or natural gas that move in as they room released from various other rock units. This provides the dolomite a reservoir rock and also a target of oil and also gas drilling.

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