Which of the following is not a mineral of boron ?

Options

A. Colemanite
B. Kernite
C. Boric anhydride
D. Borax

Answer

To determine which of the following is not a mineral of boron, we need to analyze each compound listed in the options.

### Step-by-Step Solution:

1. **Identify the Compounds**: We need to look at the compounds provided in the options and identify their chemical formulas and whether they are recognized as boron minerals.

2. **Analyze Colemanite**:
- Colemanite has the chemical formula Ca2B6O11·5H2O.
- It is known to be a boron ore.

3. **Analyze Carnite**:
- Carnite has the chemical formula Na2B4O7·4H2O.
- It is also recognized as a boron ore.

4. **Analyze Boric Anhydride**:
- Boric anhydride has the chemical formula B2O3.
- This compound is formed when orthoboric acid is heated and is not considered a mineral or ore of boron.

5. **Analyze Borax**:
- Borax, also known as tinkle, has the chemical formula Na2B4O7·10H2O.
- It is a well-known boron mineral.

6. **Conclusion**:
- Among the options analyzed, boric anhydride (B2O3) is not a mineral of boron. Therefore, the correct answer is C (boric anhydride).

### Final Answer:
C. Boric anhydride is not a mineral of boron.

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