Geol 103: Physical Properties of Minerals

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Questions and Answers

Which factor primarily influences the hardness of a mineral?

The temperature of the environment

The size of the mineral

The mineral's color

The type of chemical bonds present (correct)

What is the correct reason for testing only on fresh mineral surfaces?

To prevent scratches from previous tests (correct)

To determine the mineral's age

To enhance the mineral's visual appearance

To avoid introducing impurities

How is cleavage in minerals defined?

By the tendency to break in any direction

By the surface appearance of the mineral

By the color and texture of the mineral

By the ability to split easily in specific directions (correct)

Which of the following is NOT a characteristic for determining the cleavage of a mineral?

Chemical composition of the mineral Signup and view all the answers

What is suggested as a good practice when testing the hardness of minerals?

Scratch both minerals against each other Signup and view all the answers

What type of twinning involves a definite composition surface?

Contact twins Signup and view all the answers

Which type of twin is characterized by repeated twins that are not parallel?

Cyclic twins Signup and view all the answers

In twinning, what is the term used for rotation about a crystal direction?

Twin axis Signup and view all the answers

What describes polysynthetic twins?

Repeated twins are parallel Signup and view all the answers

Which statement about twin centers is correct?

They involve inversion about a point. Signup and view all the answers

What term describes the tendency of a mineral to break or split easily in certain directions?

Cleavage Signup and view all the answers

Which type of cleavage allows a mineral to break along one direction?

Sheet Signup and view all the answers

What type of fracture exhibits a smooth, curved surface?

Conchoidal Signup and view all the answers

What does effervescence indicate in a mineral?

Reaction with acid Signup and view all the answers

Which property describes a mineral's ability to transmit light?

Diaphaneity Signup and view all the answers

Which of the following fractures shows fibers or splinters?

Fibrous Signup and view all the answers

What does ferromagnetic indicate regarding a mineral's properties?

Strongly magnetic Signup and view all the answers

Which of the following forces causes a mineral to acquire an electric charge when subjected to mechanical stress?

Piezoelectricity Signup and view all the answers

What is the term for the resistance of a mineral to breaking or tearing?

Tenacity Signup and view all the answers

Halite is characterized by which distinctive property?

Salty taste Signup and view all the answers

What primarily determines the color of a mineral?

The chemical composition and structure Signup and view all the answers

Which term describes the appearance of a mineral's surface in reflected light?

Luster Signup and view all the answers

What is meant by the term 'habit' in mineralogy?

The crystal's general shape Signup and view all the answers

What is the purpose of the Mohs Hardness Scale?

To compare the relative hardness of minerals Signup and view all the answers

Which mineral has a hardness of 3.5 on the Mohs Scale?

Copper Signup and view all the answers

In terms of mineral color, what role do trace elements play?

They create color centers due to structural defects Signup and view all the answers

What is the 'streak' of a mineral?

The color of the mineral in powdered form Signup and view all the answers

Why are optical methods used for testing hardness in some minerals?

They allow testing without damaging the sample Signup and view all the answers

A mineral exhibits a strong pleochroism. This would imply which of the following?

It changes color depending on the angle of light incidence Signup and view all the answers

Which of these minerals is characterized by the presence of the Cr3+ ion and exhibits a green color?

Emerald Signup and view all the answers

What is the primary reason for differences in the color of an identical mineral sample?

Presence of impurities and trace elements Signup and view all the answers

Which mineral is commonly used as a reference point for a hardness of 7 on the Mohs scale?

Quartz Signup and view all the answers

If a mineral has a metallic luster, what can be inferred about its surface?

It is opaque to light Signup and view all the answers

Which of the following is NOT a method for measuring mineral hardness?

Donné Method Signup and view all the answers

Study Notes

Physical Properties of Minerals

Color is determined by the wavelengths of light that a mineral reflects, influenced by mineral chemistry and structural factors.
Streak is the color of a mineral when powdered, providing consistent identification.
Luster refers to the appearance of a mineral's surface in reflected light, important for mineral classification.
Habit describes the general shape of a crystal, including forms such as dendritic, botryoidal, micaceous, bladed, acicular, and massive.

Hardness

Hardness measures a mineral's resistance to scratching, assessed using the Mohs Hardness Scale (1 to 10).
Talc (1) to Diamond (10) serve as benchmarks for hardness, with various minerals corresponding to common objects for practical comparison.
Knoop and Vickers methods provide absolute hardness values, suitable for different specimen types.

Cleavage and Fracture

Cleavage indicates the tendency of a mineral to break along specific planes, characterized by the number and quality of these planes.
Fracture is the surface appearance when a mineral does not cleave; varieties include conchoidal, fibrous, hackly, and uneven.

Other Properties

Effervescence occurs when carbonate minerals react with acid, producing CO2 gas.
Diaphaneity describes a mineral's ability to transmit light, classified as opaque, translucent, or transparent.
Iridescence results from interference of light, creating shimmering colors.
Magnetism can be ferromagnetic, paramagnetic, or diamagnetic, indicating different magnetic properties.
Piezoelectricity and pyroelectricity refer to the generation of electric charge in response to mechanical stress or temperature changes, respectively.

Specific Gravity and Tenacity

Specific gravity is the density ratio of a mineral compared to water, important for mineral identification.
Tenacity reflects a mineral's resistance to breaking, crushing, bending, or tearing, indicating structural integrity.

Twinning

Twinning involves crystallographically-controlled intergrowths of two or more crystals, resulting in unique compositions and orientations.
Types of twins include contact, penetration, polysynthetic, and cyclic, each defined by specific attribute patterns and orientations.

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Description

This quiz covers the physical properties of minerals, including color, streak, luster, habit, hardness, and cleavage. Understanding these properties is essential for identifying and classifying minerals in Geol 103: Elementary Mineralogy. Prepare to test your knowledge on these fundamental concepts.