What is the Difference Between Gypsum and Phosphogypsum

Minerals are naturally occurring solid crystals which have a fixed chemical makeup. They are mined to be used in everyday life or in industries. Gypsum is one such mineral. Phosphogypsum is a substance that is very similar to gypsum in its chemical composition. However, gypsum and phosphogypsum are not the same.

What is the difference between gypsum and phosphogypsum? Gypsum is a natural mineral, whereas phosphogypsum is a by-product of fertilizer production.

Key Areas Covered

1. What is Gypsum 
      – Definition, Features 
2. What is Phosphogypsum
      – Definition, Features 
3. Similarities Between Gypsum and Phosphogypsum
      – Outline of Common Features
4. Difference Between Gypsum and Phosphogypsum
      – Comparison of Key Differences
5. FAQ: Gypsum and Phosphogypsum
      – Frequently Asked Questions

Key Terms

Gypsum, Phosphogypsum

Difference Between Gypsum and Phosphogypsum - Comparison Summary

What is Gypsum

Gypsum is a naturally occurring mineral having the chemical formula CaSO4·2H2O. Calcium is the main element of gypsum, providing its fire resistance properties. When heated, gypsum loses water and forms the anhydrite. Gypsum is present in many locations all around the Earth, such as evaporite beds, sedimentary rocks, hot springs, and volcanic vents.


There are many applications of gypsum. It is mainly used in the construction industry. When crushed and processed, it becomes the core of drywall, which is used to make walls and ceilings. It is also used in plasters, providing structural strength and smoothness. In agriculture, gypsum is used as a soil conditioner. Here, it is in powdered form. The purpose is to add essential calcium and sulfur to plants to promote plant growth. Due to the fire-resistant properties of gypsum, it is also useful in the manufacture of fireproofing materials. Additionally, gypsum is present in chalk. It is also useful in the food industry as a food additive to adjust the acidity.

What is Phosphogypsum

Phosphogypsum is a by-product that is generated during the production of fertilizer. Unlike natural gypsum, phosphogypsum contains trace amounts of radioactive elements such as radon and radium from the phosphate rock used in fertilizer production.


Phosphogypsum is used in road construction, specialized cement, backfilling, and mine reclamation. However, the storage of large stocks of phosphogypsum in containment ponds or landfills raises concerns about environmental contamination. Hence, people should use effective management strategies when handling phosphogypsum.

Similarities Between Gypsum and Phosphogypsum

  • Both mainly consist of calcium sulfate dihydrate.
  • Both gypsum and phosphogypsum are white or light-colored.

Difference Between Gypsum and Phosphogypsum


  • Gypsum is a naturally occurring mineral found in rock formations or formed through the evaporation of ancient seas. Phosphogypsum is a by-product generated during the production of phosphoric acid fertilizer.


  • Gypsum has very low radioactivity, whereas phosphogypsum contains trace amounts of radioactive substances like radium and radon.


  • Gypsum is widely used in many industries, the main industry being the construction industry, whereas phosphogypsum has a relatively low usage in the industry due to its radioactivity.


Gypsum and phosphogypsum are similar chemically, except that phosphogypsum has trace elements of radioactive substances in it. Gypsum and phosphogypsum are used mainly in the construction industry, but due to its radioactivity, phosphogypsum has limited uses, unlike gypsum.

FAQ: Gypsum and Phosphogypsum

1. Is phosphogypsum the same as gypsum?

No, phosphogypsum is not the same as gypsum. Phosphogypsum contains trace amounts of radioactive substances whereas gypsum has a relatively very low radioactivity. Hence, phosphogypsum is not much used in the industries unlike gypsum.

2. What are the types of gypsum?

There are two types of gypsum, natural gypsum and synthetic gypsum. Natural gypsum exists in various forms depending on its formation and crystal structure, such as massive gypsum, satin spar, selenite, and crystal gypsum.

3. Why is gypsum added to cement?

When water is mixed with cement, a chemical reaction causes the cement to harden.  This reaction happens faster without gypsum, leading to difficulty in working with cement. Therefore, gypsum is added to cement in order to control its setting time.

4. Does gypsum dissolve in water?

Gypsum is moderately soluble in water. This means it will dissolve to a certain extent. At room temperature (25°C), gypsum dissolves in water at a concentration of around 2.0-2.5 grams per liter (g/L).

5. What are the uses for phosphogypsum?

Phosphogypsum has limited usage in the industry due to the presence of radioactivity in it. It is used in road construction, agriculture, backfilling, and rare earth element extraction.


1. “Phosphogypsum.” Encyclopedia Britannica. 
2. “Gypsum.” Science Direct.

Image Courtesy:

1. “Cristales cueva de Naica” By Alexander Van Driessche – Gaianauta received this from Alexander Van Driessche via Email. (CC BY 3.0) via Commons Wikimedia
2. “GypStack” via Wikimedia Commons

About the Author: Hasini A

Hasini is a graduate of Applied Science with a strong background in forestry, environmental science, chemistry, and management science. She is an amateur photographer with a keen interest in exploring the wonders of nature and science.

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