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Are you as curious about dolomite as I am? Is dolomite a stone? Can I mine gold from dolomite? How can I find dolomite in the wild? What is the difference between dolomite and marble? This article will tell you the truth about dolomite in detail.

What is dolomite?

Dolomite, a widely used non-metallic mineral, has a rather complex chemical composition. The main component of dolomite is calcium magnesium carbonate, with the chemical formula CaMg (CO3) 2. In the theoretical chemical composition, CaO accounts for 30.4%, MgO accounts for 21.7%, and CO2 accounts for 47.9%.

Dolomite is worth noting that the magnesium element in dolomite can be replaced by elements such as iron, manganese, cobalt, and zinc, while the calcium element can be replaced by elements such as lead and sodium. When the number of iron or manganese atoms exceeds that of magnesium, this dolomite is specially named ankerite or manganese dolomite.

Therefore, dolomite is a non-metallic ore and rock.

Mineralogists point out that ideal dolomite in the mineralogical sense refers to Mg:Ca (mol%:mol%) = 50:50, and the Ca layers and Mg layers in the crystal structure are arranged alternately with the CO layers along the c-axis, thus having a cationic ordered superstructure (also called ordered dolomite).

Is dolomite a stone?

Strictly speaking, dolomite is not a stone. Dolomite is a mineral, but it can form rocks. Dolomite is the main mineral component of dolomite. Dolomite is a sedimentary rock composed of dolomite minerals, often coexisting with rocks such as limestone and shale.
From the perspective of scientific classification:
The difference between minerals and rocks
• Minerals are naturally occurring inorganic solids with a definite chemical composition and crystal structure. Dolomite meets this definition and is a single mineral.
• Rocks are aggregates composed of one or more minerals. For example, dolostone is a sedimentary rock with dolomite as the main component, which belongs to the category of “stone”.

Dolomite is a mineral, a specific component of the broad concept of “stone”. It can only be called a “stone” in a narrow sense when it combines with other minerals to form rocks (such as dolomite).

Properties of Dolomite

Color of Dolomite: Usually white, off-white or light yellow, it may be light brown or pink when it contains iron impurities. Pure dolomite is colorless and transparent (called “Iceland spar”), but it is rare in nature.

• Hardness of Dolomite: Mohs hardness is 3.5–4, between calcite (3) and fluorite (4). It can be scratched with a knife, but not by a copper coin.
• Dolomite density: The theoretical density is 2.8–2.9 g/cm³, and the actual sample may be slightly higher due to impurities.
• Luster of Dolomite: Glass luster or silk luster (when the particles are small or fibrous aggregates).
• Stability of Dolomite: Chemically stable at room temperature and pressure, but can decompose into calcium oxide (CaO) and magnesium oxide (MgO) at high temperature.
• Water absorption of Dolomite: It does not absorb water, but the surface may become loose due to weathering.
• Thermal stability of dolomite: decomposes when heated to about 900°C, producing calcium oxide, magnesium oxide and carbon dioxide.
• Transparency of dolomite: transparent to translucent, pure crystals can transmit light (Iceland spar).
• Melting point of dolomite: melting point is about 2572°C, used for refractory materials (such as steelmaking furnace lining).
• Electrical properties of dolomite: non-conductive, but weak conductivity may be generated at high temperatures due to ion migration.

What are the uses of dolomite?

As an important calcium and magnesium resource, dolomite has various forms of products and can be processed in different ways and is widely used in metallurgy, magnesium, refractory materials, building materials, chemicals, agriculture, environmental protection and other fields.

After processing, dolomite has 8 common application forms.

1. Block dolomite: Mainly used in the metallurgical industry, as a flux in steel smelting, it helps to reduce the melting point of slag and improve the fluidity of slag, thereby improving smelting efficiency.

2. Sintered dolomite: Dolomite is heated to a certain temperature to partially melt, and then cooled and hardened. The product obtained in this way has higher strength and stability and is suitable for refractory materials and metallurgical fluxes.

3. Fused dolomite: Dolomite is melted and solidified in a high-temperature electric arc furnace. This product has higher purity and is mainly used to produce high-quality refractory materials.

4. Lightly burned dolomite: also known as active dolomite, it is calcined at a lower temperature to make it have a higher reactivity, and is often used in agriculture to adjust soil pH.

5. Dolomite powder: It is made by mechanically crushing dolomite ore. According to the different particle sizes, there are mainly dolomite ultrafine powder 140 mesh, 325 mesh, 600 mesh, 1000 mesh, and 1600 mesh. It is used as filler or reinforcement material in coatings, plastics, rubber and other industries.

6. Dolomite brick: Dolomite is mixed with other refractory materials and pressed and sintered to build and repair the lining of high-temperature furnaces.

7. Dolomite sand: Dolomite particles after screening and grading are mainly 6-10 mesh, 10-20 mesh, 20-40 mesh, 40-80 mesh, and 80-120 mesh, which can be used as concrete aggregate or ground paving materials in the construction industry.

8.Dolomite pellets: Dolomite powder is pressed into spherical shapes by adding a binder, which is easy to transport and use. It is often used in steel production and the chemical industry.

Is dolomite marble or limestone?

Dolomite, limestone and marble are all common building and industrial materials, but they have obvious differences in chemical composition, physical properties and uses. The following will introduce the differences between marble, limestone and dolomite in detail from these three aspects.

Dolomite VS Limestone VS Marble

Differences in chemical composition

1. Dolomite: The main component is calcium magnesium carbonate (CaCO3·MgCO3), with a content of about 75% to 90%, and also contains a small amount of iron, manganese, silicon and other elements.

2. Limestone: The main component is also calcium carbonate (CaCO3), with a content of about 90% to 95%, but usually contains a small amount of impurities such as magnesium carbonate (MgCO3) and calcium oxide (CaO).

3. Marble: The main component is calcium carbonate (CaCO3), with a content of about 50% to 90%, and also contains a small amount of magnesium, iron, manganese and other elements.

Differences in physical properties

1. Dolomite: The color is mainly white or off-white, the surface gloss is low, the hardness is moderate, and it is relatively easy to process.

2. Limestone: The color is mainly gray or off-white, the surface gloss is low, the hardness is moderate, and it is relatively easy to process.

3. Marble: The colors are rich and varied, including white, gray, black, red, green and other colors, the surface gloss is high, the hardness is moderate, and it is relatively easy to process.

Uses

1. Dolomite: Due to its good heat resistance and chemical stability, it is often used in metallurgy, ceramics, glass, chemical industry and other fields.

2. Limestone: Due to its abundant resources and low cost, it is often used in building materials, cement, glass, metallurgy and other fields.

3. Marble: Due to its beautiful appearance and good processing performance, it is often used in architectural decoration, sculpture, handicraft production and other fields.

Dolomite exists in the following forms in nature:

1. Sedimentary dolomite

Syngenetic deposition: Dolomite may be formed directly during the deposition process, but this origin is controversial. For example, in the supratidal zone, seawater moves upward through coastal sediments and evaporates at the sediment-air interface to form dolomite sediments.
Replacement deposition: Dolomite is more likely to be formed through metasomatism, that is, primary calcium carbonate minerals (such as calcite) are replaced by magnesium-containing fluids and gradually transformed into dolomite.

2. Hydrothermal dolomite

Hydrothermal metasomatism: In a high-temperature and high-pressure hydrothermal environment, dolomite can be formed through hydrothermal metasomatism. This type of dolomite is usually associated with metal deposits, such as those found in some veins.
Mixed water mode: In some areas, after groundwater mixes with seawater, the enrichment of magnesium ions and sulfate ions may promote the formation of dolomite.

3. Microbial-induced dolomite

Microbial action: Studies in recent years have shown that microorganisms may play a key role in the formation of dolomite. Microorganisms can change the chemical conditions of the surrounding environment through metabolic activities and promote the precipitation of dolomite. For example, in some sedimentary environments rich in organic matter, microbial activity can promote the formation of dolomite.

4. Secondary dolomite

Secondary replacement: In the later geological processes of rocks, such as metamorphism or weathering, the original carbonate minerals may be replaced by dolomite. This secondary dolomite usually has complex structural and compositional changes.

5. Special environment dolomite

Extreme environment: In some special geological environments, such as salt lakes, deep-sea deposits, etc., dolomite may also be formed through special chemical processes. For example, in salt lakes, due to high salinity and special chemical environments, the precipitation of dolomite may be promoted.

Can I mine gold from dolomite?

From the current geological research and mineral resource development, dolomite itself does not contain gold, so gold cannot be directly obtained by mining dolomite. The following is a detailed explanation:

Composition and properties of dolomite

Dolomite is a carbonate mineral with a chemical formula of CaMg(CO₃)₂, mainly composed of calcium, magnesium and carbonate. It is the main mineral component of dolomite and dolomitic limestone, and is usually associated with minerals such as calcite, magnesite, and quartz.

Distribution and mining of gold

Gold is mainly distributed in specific veins in the earth’s crust, usually associated with minerals such as quartz and sulfides.
Gold mining is mainly concentrated in gold deposits, such as vein gold and placer gold, rather than carbonate mineral deposits.

Association between dolomite and gold mining

– Although some other minerals may be associated with dolomite deposits, there is currently no evidence that economically mineable gold exists in dolomite deposits.
– Dolomite is mainly used in metallurgy, chemical industry, building materials and other fields, rather than precious metal mining.

Therefore, it is unrealistic to mine gold from dolomite deposits. Gold mining still needs to rely on specialized gold mine resources.

The unsolved mystery of dolomite

The sedimentary rock records of the Precambrian-Early Paleozoic contain large-scale (ordered) dolomite deposits, but there is a lack of large-scale dolomite deposits in the oceans after and in the modern era. It is difficult to synthesize (ordered) dolomite at normal temperature and pressure.

The cause of large-scale ordered dolomite deposition in geological history has become an unsolved mystery, which is also commonly known as the “Dolomite Mystery”/”Dolomite Problem” by geologists!