Which is not the correct statement ?

Options

A. Cassiterite and haematite are concentrated by hydraulic washing.
B. Pure `Al_(2)O_(3)` is obtained from the bauxite ore by leaching in the Baeyer's process.
C. Sulphide ore is concentrated by calcination method.
D. Roasting can convert sulphide into oxide or sulphate and part of sulphide may also act as a reducing agent.

Explanation

To determine which statement is not correct regarding the concentration of ores and the processes involved, we can analyze the statements provided in the video transcript step by step.

### Step-by-Step Solution:

1. **Understanding Hydraulic Washing**:
- Hydraulic washing is a method used for the concentration of ores based on the difference in specific gravities of the ore and impurities (gangue).
- This method is effective for separating heavier metallic ores from lighter impurities.

**Hint**: Recall that hydraulic washing relies on the specific gravity differences between materials.

2. **Correctness of Statements**:
- The first statement mentions that hydraulic washing is used for the concentration of ores. This is true.
- The second statement refers to obtaining pure aluminum oxide through the Bayer process, which involves leaching. This is also true.

**Hint**: Identify processes associated with specific metals and their extraction methods.

3. **Sulfide Ore Concentration**:
- The third statement claims that sulfide ore is concentrated by the calcination method. This is false.
- Calcination is used for carbonate ores, while sulfide ores are concentrated through roasting, which occurs in the presence of oxygen.

**Hint**: Differentiate between calcination and roasting processes and their applications.

4. **Roasting Process**:
- The fourth statement discusses roasting converting sulfide ores into oxides or sulfates, which is true. It also mentions that some sulfides can act as reducing agents.

**Hint**: Remember the chemical transformations that occur during roasting.

5. **Conclusion**:
- The statement that is not correct is the one that claims sulfide ore is concentrated by the calcination method. Instead, sulfide ores are concentrated by roasting.

### Final Answer:
The statement that is not correct is: "Sulfide ore is concentrated by calcination method."