Question

Which one of the following minerals belongs to the cubic (isometric) crystal system?

• A. Quartz
• B. Orthoclase
• C. Galena
• D. Gypsum

Hint:

Common cubic system minerals include {Galena, Halite, Pyrite, and Magnetite}. Memorizing these helps in quick elimination.

Answer 1

The Correct Option is C

Step 1: Understanding the cubic crystal system.
The cubic (or isometric) crystal system is characterized by three crystallographic axes of equal length that intersect each other at right angles. Minerals belonging to this system commonly show cubic or octahedral crystal forms.
Step 2: Evaluating the given options.
(A) Quartz: Quartz belongs to the hexagonal (trigonal) crystal system, not the cubic system.
(B) Orthoclase: Orthoclase feldspar crystallizes in the monoclinic system.
(C) Galena: Galena crystallizes in the cubic (isometric) crystal system and commonly forms cubic crystals.
(D) Gypsum: Gypsum belongs to the monoclinic crystal system.
Step 3: Conclusion.
Among the given minerals, only Galena belongs to the cubic (isometric) crystal system. Therefore, the correct answer is (C) Galena.