Which of the following mineral contains calcium as well as magnesium ?

Options

A. Tridymite
B. Aragonite
C. Dolomite
D. Camalite

Answer

To determine which mineral contains both calcium and magnesium, we will analyze each of the given options step by step.

### Step 1: Analyze Tridymite
- **Description**: Tridymite is a polymorph of silica.
- **Chemical Formula**: SiO2
- **Conclusion**: Tridymite does not contain calcium or magnesium.

### Step 2: Analyze Aragonite
- **Description**: Aragonite is a carbonate mineral.
- **Chemical Formula**: CaCO3 (calcium carbonate)
- **Conclusion**: Aragonite contains calcium but does not contain magnesium.

### Step 3: Analyze Dolomite
- **Description**: Dolomite is an anhydrous carbonate mineral.
- **Chemical Formula**: CaMg(CO3)2
- **Conclusion**: Dolomite contains both calcium and magnesium.

### Step 4: Analyze Carnallite
- **Description**: Carnallite is an evaporite mineral.
- **Chemical Formula**: KMgCl3·6H2O (hydrated potassium magnesium chloride)
- **Conclusion**: Carnallite contains magnesium but does not contain calcium.

### Final Conclusion
After analyzing all the options:
- **Tridymite**: No calcium or magnesium.
- **Aragonite**: Contains calcium only.
- **Dolomite**: Contains both calcium and magnesium.
- **Carnallite**: Contains magnesium only.

Thus, the mineral that contains both calcium and magnesium is **Dolomite**.

### Answer:
**Dolomite** (Option 3)

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