In which of the following pairs, both the minerals are oxides ?

Options

A. Sylvine, saltpetre
B. Casseterite, litharge
C. Siderite, corundum
D. Cuprite, tinstone

Answer

To determine which pairs of minerals are both oxides, we will analyze each pair and identify their chemical formulas.

### Step-by-Step Solution:

1. **Identify the minerals in each pair:**
- Pair 1: Sylvine and Saltpeter
- Pair 2: Cassiterite and Letharge
- Pair 3: Siderite and Corundum
- Pair 4: Cuprite and Tinstone

2. **Determine the chemical formulas of each mineral:**
- **Sylvine (KCl)**: This is a potassium chloride mineral, which is not an oxide.
- **Saltpeter (KNO3)**: This is potassium nitrate, which is also not an oxide.

Thus, **Pair 1** (Sylvine and Saltpeter) does not consist of oxides.

3. **Next, analyze Pair 2:**
- **Cassiterite (SnO2)**: This is a tin oxide.
- **Letharge (PbO)**: This is a lead oxide.

Therefore, **Pair 2** (Cassiterite and Letharge) consists of both minerals being oxides.

4. **Now, check Pair 3:**
- **Siderite (FeCO3)**: This is an iron carbonate, which is not an oxide.
- **Corundum (Al2O3)**: This is an aluminum oxide.

Hence, **Pair 3** (Siderite and Corundum) does not consist of both minerals being oxides.

5. **Finally, analyze Pair 4:**
- **Cuprite (Cu2O)**: This is a copper oxide.
- **Tinstone (SnO2)**: This is a tin oxide.

Thus, **Pair 4** (Cuprite and Tinstone) consists of both minerals being oxides.

### Conclusion:
The pairs where both minerals are oxides are:
- Pair 2: Cassiterite and Letharge
- Pair 4: Cuprite and Tinstone

### Final Answer:
The correct pairs where both minerals are oxides are **Cassiterite and Letharge** and **Cuprite and Tinstone**.

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