Question:
A muscovite has the following composition in which iron is ferrous. The amount of ‘Al’ in the tetrahedral site is ________ (per formula unit). (Round off to two decimal places.)
Muscovite composition: KAl2.50Fe0.25Si3.25O10(OH)2
A muscovite has the following composition in which iron is ferrous. The amount of ‘Al’ in the tetrahedral site is ________ (per formula unit). (Round off to two decimal places.)
Muscovite composition: KAl2.50Fe0.25Si3.25O10(OH)2
Muscovite composition: KAl2.50Fe0.25Si3.25O10(OH)2
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For phyllosilicates: Tetrahedral site = 4 cations (Si + Al); Octahedral site = remaining Al/Fe/Mg.
Updated On: Dec 6, 2025
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Correct Answer: 0.75
Solution and Explanation
Step 1: Tetrahedral site cations.
Tetrahedral sites are mainly occupied by Si and Al (T-site). Total occupancy = 4 atoms.
Step 2: Given Si = 3.25.
Hence, T-site Al = 4 – 3.25 = 0.75.
Step 3: Conclusion.
Tetrahedral Al = 0.75 per formula unit.
Tetrahedral sites are mainly occupied by Si and Al (T-site). Total occupancy = 4 atoms.
Step 2: Given Si = 3.25.
Hence, T-site Al = 4 – 3.25 = 0.75.
Step 3: Conclusion.
Tetrahedral Al = 0.75 per formula unit.
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