Which one of the following minerals has crystallographic axes \( a_1 = a_2 \neq c \) and all interaxial angles equal to 90°?
Show Hint
- Beryl
- Barite
- Plagioclase
- Zircon
The Correct Option is D
Solution and Explanation
\( a_1 = a_2 \neq c \)
All interaxial angles are 90°.
Among the listed minerals:
Beryl: Has an hexagonal crystal system.
Barite: Has an orthorhombic system, not tetragonal.
Plagioclase: Belongs to the triclinic system.
Zircon: Has a tetragonal crystal system with \( a_1 = a_2 \neq c \) and interaxial angles of 90°.
Step 2: Conclusion
Option (D) Zircon is the correct answer, as it fits the conditions of the tetragonal system described.
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