Question

Consider the statements regarding the internal structure of minerals

1. I. Crystal structure is naturally restricted if the mineral's growth is inhibited.
2. II. Amorphous minerals are those that have developed independently in nature.
3. III. "Luster" and "Transparency" are synonyms for the same physical property.

• A. All
• B. 1 only
• C. 3 only
• D. 1, 2

Answer 1

Answer:

B. 1 only

Understanding Mineral Structures and Properties

This explanation focuses on key concepts related to the internal structure and observable properties of minerals, crucial for competitive exams.

Crystal Structure and Mineral Growth

• Statement I: Crystal structure is naturally restricted if the mineral's growth is inhibited. This statement is correct. The internal arrangement of atoms within a mineral defines its crystal structure. When a mineral grows freely in an open space, it can develop well-defined crystal faces, exhibiting its characteristic habit. However, if the mineral's growth is constrained by surrounding materials or lack of space, its ability to form these perfect external shapes is limited, even though the internal atomic arrangement (the crystal lattice) might still be present. External restriction leads to inhibited crystal development.

Amorphous Minerals

• Statement II: Amorphous minerals are those that have developed independently in nature. This statement is incorrect. Amorphous minerals (or more accurately, amorphous solid substances that are sometimes loosely referred to as minerals) lack a regular, repeating internal atomic arrangement. They do not possess a true crystal structure. Examples often cited include obsidian (volcanic glass) and opal. The term "developed independently in nature" is too broad and doesn't specifically define amorphous materials; many crystalline minerals also develop independently in nature. The defining characteristic of amorphous substances is the absence of crystallinity.

Distinguishing Physical Properties

• Statement III: "Luster" and "Transparency" are synonyms for the same physical property. This statement is incorrect. Luster refers to the way light interacts with the surface of a mineral, describing its shininess (e.g., metallic, vitreous, dull). Transparency, on the other hand, describes how much light can pass through a mineral. Minerals can be transparent (light passes through), translucent (light passes through but is scattered), or opaque (no light passes through). These are distinct physical properties.