Which of the following aluminium minerals does not contain oxygen ?

Options

A. Bauxite
B. Diaspore
C. Gibsite
D. Cryolite

Answer

To solve the question of which aluminium mineral does not contain oxygen, we will analyze the formulas of the given minerals step by step.

### Step 1: Identify the minerals and their formulas
1. **Bauxite**: The formula for Bauxite is \( \text{Al}_2\text{O}_3 \cdot \text{NH}_2\text{O} \).
2. **Diaspore**: The formula for Diaspore is \( \text{AlOOH} \).
3. **Gibbsite**: The formula for Gibbsite is \( \text{Al(OH)}_3 \).
4. **Cryolite**: The formula for Cryolite is \( \text{Na}_3\text{AlF}_6 \).

### Step 2: Analyze the presence of oxygen in each mineral
- **Bauxite** contains oxygen in the form of \( \text{Al}_2\text{O}_3 \).
- **Diaspore** contains oxygen in the form of \( \text{AlOOH} \).
- **Gibbsite** contains oxygen in the form of \( \text{Al(OH)}_3 \).
- **Cryolite** does not contain oxygen; its formula \( \text{Na}_3\text{AlF}_6 \) consists of sodium, aluminium, and fluorine only.

### Step 3: Conclusion
From the analysis, we can conclude that the mineral that does not contain oxygen is **Cryolite**.

### Final Answer
The aluminium mineral that does not contain oxygen is **Cryolite**.

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