Aluminium (Al) can occur in both tetrahedral and octahedral co-ordinations in silicates. The amount of octahedral Al in a pyroxene crystal of composition Mg₁.₄Fe₀.₄Al₀.₈Si₂O₆ is (give answer in one decimal place).
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Solution and Explanation
This question asks for the amount of octahedral aluminium (Al) in a pyroxene crystal of a specific composition.
Step 2: Analyzing the composition.
In the given formula Mg₁.₄Fe₀.₄Al₀.₈Si₂O₆, Al is present in the octahedral site. The amount of Al is directly given as 0.8 in the formula, which is the amount in the octahedral co-ordination.
Step 3: Conclusion.
The correct answer is 0.8, as this is the amount of octahedral aluminium in the crystal.
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