Problem 6 List and define the principal ph... [FREE SOLUTION]

Chapter 5: Problem 6

List and define the principal physical properties used to identify a mineral. (E)

Short Answer

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The principal physical properties used to identify a mineral include: 1. Color: The visible hue of a mineral, although it can be unreliable due to impurities. 2. Luster: The way a mineral reflects light, categorized as metallic or non-metallic. 3. Hardness: The mineral's resistance to scratching, measured using Mohs scale (1-10). 4. Streak: The color of a mineral's powdered form, determined by rubbing it across a streak plate. 5. Crystal Form: The natural shape of a mineral determined by its internal crystalline structure. 6. Cleavage: A mineral's tendency to break along flat, smooth surfaces due to weak crystal structure points. 7. Fracture: How a mineral breaks when it doesn't exhibit cleavage, occurring irregularly. 8. Specific Gravity: A measure of a mineral's density relative to water, comparing the mass of the mineral to the mass of an equal volume of water.

Step by step solution

1. Color

: Color is one of the simplest physical properties to observe and can be used as a basic characteristic to help identify a mineral. However, it is not always reliable as some minerals can occur in various colors due to impurities.

2. Luster

: Luster refers to how a mineral reflects light. There are two main categories of luster: metallic and non-metallic. A metallic luster has a shiny, reflective surface, like metal, while non-metallic lusters can be described as glassy, pearly, silky, etc.

3. Hardness

: Hardness is a measure of how easily a mineral can be scratched. It is determined based on Mohs scale of mineral hardness, which assigns a number from 1 (softest) to 10 (hardest) based on a mineral's ability to scratch another mineral. For example, Talc has a hardness of 1 and Diamond has a hardness of 10.

4. Streak

: Streak refers to the color of the powdered form of a mineral. It is determined by rubbing the mineral across a streak plate (unglazed porcelain) and observing the color of the residue left behind. Streak is often more reliable than color for identifying minerals, as it is less affected by impurities.

5. Crystal Form

: Crystal form refers to the mineral's natural shape when it forms in optimal conditions. The arrangement of atoms within a mineral's crystalline structure determines its crystal form. By examining a crystal's form, it is possible to identify the mineral and gain insight into its internal structure.

6. Cleavage

: Cleavage refers to a mineral's tendency to break along flat, smooth surfaces. When a mineral has good cleavage, it breaks along consistent planes due to weak points in its crystal structure. Cleavage can be described based on how many planes it occurs along and the angles between those planes.

7. Fracture

: Fracture is a measure of how a mineral breaks when it does not exhibit cleavage. Unlike cleavage, fractures occur in an irregular manner. Types of fracture include conchoidal (shell-like, smooth curves), splintery, and uneven.

8. Specific Gravity

: Specific gravity is a measure of a mineral's density relative to water. It is determined by dividing the mass of the mineral by the mass of an equal volume of water. Minerals with a higher specific gravity feel heavier for their size compared to those with a lower specific gravity.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Physical Properties of Minerals

Minerals can be identified through a variety of physical properties. These properties are observable characteristics that help us distinguish one mineral from another. Among the most common properties used in mineral identification are:

Color: Although the color can be easily noticed, it is not the most reliable indicator due to variations caused by impurities.
Luster: This refers to the way a mineral reflects light. It can range from metallic and shiny to non-metallic like glass or pearl.
Streak: The color of the mineral in powdered form, observed by rubbing it on a streak plate, usually offers more consistency than the surface color.
Specific Gravity: This property measures the density of the mineral relative to water, influencing how heavy the mineral feels for its size.

Each of these properties provides unique insights into the identity and nature of the mineral, aiding in their classification.

Mohs Scale of Mineral Hardness

The Mohs scale of mineral hardness is a critical tool for mineral identification. It ranks minerals on a scale from 1 to 10, determining how easily a mineral can be scratched by another. This scale provides:

Standard of Comparison: Minerals are compared against a set of standard minerals with known hardness.
Relative Hardness: With 1 being the softest, like talc, and 10 being the hardest, like diamond, minerals are juxtaposed to evaluate scratch resistance.
Practical Test: If a mineral can scratch another, it indicates it is harder. Conversely, if it can be scratched, it is softer.

This testing method helps in narrowing down possibilities when identifying mineral specimens, providing direct, observable criteria for distinguishing hardness.

Crystal Structure

The crystal structure of a mineral is its atomic arrangement, determined by the mineral's unique set of atoms and bonds. Key aspects of crystal structure include:

Crystalline Shape: The external shape of a crystal gives clues about its internal atomic arrangement.
Lattice System: Minerals are organized into specific geometric arrangements called crystal lattices, including cubic, tetragonal, hexagonal, and more.
Symmetry: Crystal symmetry can offer insights into the conditions under which a mineral formed and its growth history.

Understanding crystal structure allows geologists to infer a mineral's growth conditions and chemical composition, providing a deeper understanding of the mineral's origin.

Mineral Cleavage and Fracture

Mineral cleavage and fracture describe how a mineral breaks when subjected to stress. These properties highlight the internal weaknesses and strengths within the mineral鈥檚 structure:

Cleavage: Refers to the tendency of a mineral to break along flat, smooth surfaces that reflect zones of weakness within the crystal lattice. It is characterized by distinct planes and angles.
Fracture: Occurs when a mineral lacks cleavage, resulting in more irregular breaks. Common types of fracture include conchoidal (smooth, curved surfaces), splintery, or uneven.

Both cleavage and fracture provide vital information about the mineral鈥檚 molecular arrangement and help in distinguishing between minerals with similar physical appearances.

91影视

List and define the principal physical properties used to identify a mineral. (E)

Short Answer

Step by step solution

1. Color

2. Luster

3. Hardness

4. Streak

5. Crystal Form

6. Cleavage

7. Fracture

8. Specific Gravity

Key Concepts

Physical Properties of Minerals

Mohs Scale of Mineral Hardness

Crystal Structure

Mineral Cleavage and Fracture

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