Question

Which of the following is NOT an essential property of a mineral?

• A. Natural occurrence
• B. Regular internal structure
• C. Fixed composition
• D. Solid state

Hint:

Minerals often occur as solid solutions. So, while they have a definite range of composition, it is not a single fixed formula.

Answer 1

The Correct Option is C

Step 1: Essential properties of minerals.
A mineral is defined as: - Naturally occurring, - Solid, - Inorganic, - With an ordered internal structure (crystalline), - Having a definite but not necessarily fixed chemical composition.

Step 2: Key clarification.
The composition of many minerals is not strictly fixed but varies within limits due to solid solution (e.g., plagioclase: Albite–Anorthite series).

Step 3: Conclusion.
Thus, "fixed composition" is not an essential property; instead, "definite composition within a range" is correct.

Final Answer:
\[ \boxed{\text{Fixed composition}} \]