Which of the following is not a concentration technique?

Options

A. Levigation
B. Froth-flotation
C. Leaching
D. Calcination

Answer

To determine which of the following is not a concentration technique, we will analyze each option provided: levigation, froth flotation, leaching, and calcination.

### Step-by-Step Solution:

1. **Understanding Concentration Techniques**:
- Concentration techniques refer to the processes used to remove unwanted materials from ore, thereby increasing the concentration of the desired mineral.

2. **Analyzing Each Option**:
- **Levigation**: This is a technique that involves the separation of particles based on their densities. It is commonly used to concentrate ores by removing lighter impurities.
- **Froth Flotation**: This is a widely used concentration technique where minerals are separated based on their hydrophobic properties. It is effective for separating sulfide ores from gangue.
- **Leaching**: This process involves the extraction of valuable metals from ores by dissolving them in a solvent. It is also considered a concentration technique.
- **Calcination**: This process involves heating a solid material to high temperatures in the absence of air. It is primarily used for the purification of ores by removing volatile substances and is not a concentration technique.

3. **Conclusion**:
- Among the options given, **calcination** is not a concentration technique. It is a purification process.

### Final Answer:
The option that is not a concentration technique is **calcination** (Option D).

---