WHY CACO3 IS SELECTED AS STANDARD FOR HARDNESS

Hardness is a measure of a mineral's resistance to scratching. It is one of the most important physical properties of minerals, and it is used to identify and classify them. The Mohs scale of hardness is the most widely used scale for measuring hardness. It was developed by the German mineralogist Friedrich Mohs in 1822.

The Mohs scale is a relative scale, meaning that it is based on the ability of one mineral to scratch another. The scale ranges from 1 to 10, with 1 being the softest and 10 being the hardest.

How is the Mohs Scale Used?

To use the Mohs scale, you simply try to scratch one mineral with another. If the first mineral scratches the other, then it is harder than the other. If the second mineral scratches the first, then it is harder than the first. If the two minerals do not scratch each other, then they are said to be of equal hardness.

Mohs selected ten minerals, each with a different hardness, to create his scale. The minerals are:

• Talc (hardness 1)
• Gypsum (hardness 2)
• Calcite (hardness 3)
• Fluorite (hardness 4)
• Apatite (hardness 5)
• Orthoclase (hardness 6)
• Quartz (hardness 7)
• Topaz (hardness 8)
• Corundum (hardness 9)
• Diamond (hardness 10)

Why is Calcite (CaCO3) Selected as the Standard for Hardness 3?

Calcite is a common mineral that is found in many different parts of the world. It is a relatively soft mineral, with a hardness of 3 on the Mohs scale. This makes it ideal for use as a standard for hardness.

Calcite is also a very stable mineral. It does not react with most chemicals, and it is not easily scratched. This makes it a good choice for use in a variety of applications, such as countertops, tiles, and sculptures.

Other Uses of Calcite

In addition to being used as a standard for hardness, calcite is also used in a variety of other applications. Some of the most common uses of calcite include:

• Agriculture: Calcite is used as a soil amendment to help improve soil structure and fertility.
• Construction: Calcite is used in the production of cement, concrete, and other building materials.
• Industrial: Calcite is used in the production of glass, ceramics, and other industrial products.
• Pharmaceuticals: Calcite is used in the production of some medications, such as antacids and calcium supplements.

Conclusion

Calcite is a versatile mineral with a wide range of applications. It is a common mineral that is found in many different parts of the world. It is a relatively soft mineral, with a hardness of 3 on the Mohs scale. This makes it ideal for use as a standard for hardness. Calcite is also a very stable mineral, which makes it a good choice for use in a variety of applications.

Frequently Asked Questions

1. What is the Mohs scale of hardness?
   The Mohs scale of hardness is a relative scale for measuring the hardness of minerals. It was developed by the German mineralogist Friedrich Mohs in 1822. The scale ranges from 1 to 10, with 1 being the softest and 10 being the hardest.

2. Why is calcite used as the standard for hardness 3?
   Calcite is a common mineral that is found in many different parts of the world. It is a relatively soft mineral, with a hardness of 3 on the Mohs scale. This makes it ideal for use as a standard for hardness. Calcite is also a very stable mineral, which makes it a good choice for use in a variety of applications.

3. What are some of the other uses of calcite?
   Calcite is used in a variety of applications, including:

   • Agriculture: Calcite is used as a soil amendment to help improve soil structure and fertility.
   • Construction: Calcite is used in the production of cement, concrete, and other building materials.
   • Industrial: Calcite is used in the production of glass, ceramics, and other industrial products.
   • Pharmaceuticals: Calcite is used in the production of some medications, such as antacids and calcium supplements.

4. What is the difference between hardness and toughness?
   Hardness is a measure of a mineral's resistance to scratching, while toughness is a measure of a mineral's resistance to breaking. A mineral can be hard and brittle, or it can be soft and tough. For example, diamond is a very hard mineral, but it is also brittle. Calcite is a relatively soft mineral, but it is also tough.

5. What are some other minerals that are used as standards for hardness?
   In addition to calcite, other minerals that are used as standards for hardness include:

   • Talc (hardness 1)
   • Gypsum (hardness 2)
   • Fluorite (hardness 4)
   • Apatite (hardness 5)
   • Orthoclase (hardness 6)
   • Quartz (hardness 7)
   • Topaz (hardness 8)
   • Corundum (hardness 9)
   • Diamond (hardness 10)