Gypsum

Gypsum is a sedimentary, white-colored mineral composed of hydrated calcium sulfate (CaSO₄·2H₂O), which is abundantly found in nature. Due to its crystallization water, it has numerous applications in construction and other industries. Gypsum typically forms in dry and desert regions and is found in many parts of the world, including Iran.

Properties and Characteristics of Gypsum

1. Chemical Composition: Gypsum is composed of calcium, sulfur, oxygen, and water.
2. Softness and Malleability: Gypsum is a soft material that can easily be scratched and crushed. Its hardness on the Mohs scale is about 2.
3. Color and Transparency: Gypsum is typically white or light gray, but due to impurities, it can sometimes appear in shades of yellow, pink, or brown.
4. Crystallization Water: Due to its two water molecules of crystallization, gypsum can easily lose its water at high temperatures and convert into building plaster.

Types of Gypsum

Gypsum is classified into several types, the most important of which are:

1. Gypsum (Gypsum): The most common type of gypsum, this is the naturally occurring form found in nature.
2. Anhydrite: A type of gypsum that lacks crystallization water and has a structure similar to gypsum, but without water in its composition.
3. Crystalline Gypsum or Selenite: A transparent and crystalline form of gypsum that is used in decorative industries due to its high transparency and beauty.

Production Process of Building Plaster

Building plaster is made from natural gypsum. The production process of building plaster includes the following steps:

1. Extraction: Gypsum is extracted from surface or underground mines.
2. Crushing: The extracted gypsum is crushed into smaller pieces.
3. Heating: The crushed gypsum is heated in rotary or traditional furnaces to remove its crystallization water. This process typically occurs at around 150°C.
4. Grinding and Packaging: The calcined gypsum is ground into powder and packaged for use in construction and other industries.

Applications of Gypsum

1. Construction Industry:

   • Plastering and Whitewashing Walls: Gypsum is used for coating walls and ceilings in building construction. Due to its quick drying time and paintability, it is used for interior decorations.
   • Production of Prefabricated Parts: Gypsum is used in the manufacturing of gypsum panels, lightweight blocks, and prefabricated construction parts.

2. Medical Industry:

   • Medical Plaster: Due to its moldability and fast setting time, gypsum is used in medicine for casting broken bones.

3. Cement Industry:

   • Gypsum is used as a setting regulator in the production of Portland cement.

4. Agriculture:

   • Gypsum is used to improve saline and alkaline soils. It helps in regulating the pH and improving the structure of the soil.

5. Pulp and Paper, Paint, and Rubber Industries:

   • Gypsum is used as a filler and stabilizer in the production of paper, paint, and rubber products.

Gypsum Reserves in Iran

Iran is one of the largest producers and exporters of gypsum in the world, with significant reserves of this mineral. The provinces of Semnan, Khorasan, Kerman, and Fars are among the key regions with gypsum mines in Iran. The high quality and abundance of gypsum in Iran have made the country one of the major suppliers of gypsum in global markets.

Advantages of Gypsum

1. Environmentally Friendly: Gypsum is a natural and biodegradable material that does not harm the environment.
2. Cost-Effective: Due to the abundance of gypsum in nature, its production cost is low, making it an inexpensive building material.
3. Insulation Properties: Gypsum has thermal and acoustic insulation properties, which can help reduce energy loss in buildings.
4. Ease of Use: Gypsum is easy to shape and dries quickly, making it highly valued in the construction industry.

Challenges and Limitations of Gypsum

• Low Resistance to Moisture: Gypsum easily absorbs water and deteriorates in humid environments, so its use in wet areas is limited.
• Susceptibility to Impact and Scratching: Gypsum is sensitive to impact and wear, and it can easily break or scratch under pressure.

Economic and Industrial Importance of Gypsum

Gypsum is considered a strategic mineral due to its wide use in the construction and agriculture industries. The production of gypsum and its export to neighboring countries can be a source of foreign exchange for the country. Additionally, the widespread use of gypsum in domestic construction projects has made it one of the most consumed building materials.

Overall, gypsum is one of the most important and widely used minerals in the world, and Iran, due to its rich reserves, plays a significant role in its production and export.