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Questions and Answers
What are the imaginary lines that pass through the center of a crystal called?
What are the imaginary lines that pass through the center of a crystal called?
There are three types of symmetry elements in crystallography.
There are three types of symmetry elements in crystallography.
True
What is meant by 'parameters' in the context of crystallographic axes?
What is meant by 'parameters' in the context of crystallographic axes?
The relative intercepts made by a crystal face on the three crystallographic axes.
The three crystallographic axes can be represented as ___ , ___ , and ___ for XOX', YOY', and ZOZ'.
The three crystallographic axes can be represented as ___ , ___ , and ___ for XOX', YOY', and ZOZ'.
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Match the terms related to crystallographic axes with their definitions:
Match the terms related to crystallographic axes with their definitions:
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Which of the following statements accurately describes crystallographic axes?
Which of the following statements accurately describes crystallographic axes?
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What type of crystallographic form is characterized by a set of similar faces showing identical mathematical relations with crystallographic axes?
What type of crystallographic form is characterized by a set of similar faces showing identical mathematical relations with crystallographic axes?
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In the Miller system, indices for a crystal face are derived from its parameters.
In the Miller system, indices for a crystal face are derived from its parameters.
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How many straight lines pass through a common center to define the simplest form of crystallographic axes?
How many straight lines pass through a common center to define the simplest form of crystallographic axes?
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In the isometric system, all crystals can be referred to three crystallographic axes that are of equal length and at right angles to each other.
In the isometric system, all crystals can be referred to three crystallographic axes that are of equal length and at right angles to each other.
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Name one crystal form that commonly develops in the isometric system.
Name one crystal form that commonly develops in the isometric system.
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The symmetry class in the isometric system that is commonly associated with galena type is known as the __________ class.
The symmetry class in the isometric system that is commonly associated with galena type is known as the __________ class.
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Match the following types of crystallographic forms with their descriptions:
Match the following types of crystallographic forms with their descriptions:
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Which of the following statements correctly describes the hexagonal system?
Which of the following statements correctly describes the hexagonal system?
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The trisoctahedron is one of the common forms in the hexagonal system.
The trisoctahedron is one of the common forms in the hexagonal system.
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What is the relationship between crystallographic axes in the isometric system?
What is the relationship between crystallographic axes in the isometric system?
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What is the designation for the horizontal axes in an axial diagram of the hexagonal system?
What is the designation for the horizontal axes in an axial diagram of the hexagonal system?
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In the monoclinic system, all three axes are equal in length.
In the monoclinic system, all three axes are equal in length.
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Name one common form of the monoclinic system.
Name one common form of the monoclinic system.
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In the monoclinic system, the vertical axis is designated by the letter ______.
In the monoclinic system, the vertical axis is designated by the letter ______.
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The inclined axis in the monoclinic system is referred to as which axis?
The inclined axis in the monoclinic system is referred to as which axis?
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Peat is a completely transformed form of coal.
Peat is a completely transformed form of coal.
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What is lignite and its primary use?
What is lignite and its primary use?
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Match the following terms with their descriptions:
Match the following terms with their descriptions:
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Study Notes
Crystallographic Forms
- A form is a group of similar crystal faces that have the same mathematical relationship to the crystallographic axes.
- Forms are often classified based on their relationship to the crystallographic axes, such as holohedral, hemihedral, hemimorphic, enantiomorphic, and fundamental.
- Open forms do not enclose space.
- Closed forms enclose space.
Isometric System
- The Isometric system is characterized by three crystallographic axes of equal length that are mutually perpendicular.
- All axes are interchangeable.
- There are five symmetry classes within the Isometric system, with the most common known as the galena type.
- Common forms include the cube, octahedron, dodecahedron, trisoctahedron, trapezohedron, hexaoctahedron, and tetrahexahedron.
Hexagonal System
- The Hexagonal system has three horizontal axes of equal length that intersect at 120 degrees.
- The fourth axis is vertical and perpendicular to the horizontal axes.
- The internal atomic arrangement of a mineral is reflected externally by its crystal shape.
Symmetry
- Symmetry in crystals refers to the regularity in the arrangement of faces.
- Three elements of symmetry are: planes of symmetry, axes of symmetry, and centers of symmetry.
Crystallographic Axes
- Crystallographic axes are imaginary lines passing through the center of an ideal crystal.
- These axes are used to establish mathematical relationships between the faces of a crystal.
- Crystallographic axes are defined by their lengths and angles relative to each other.
- There can be three or four axes, with different relationships.
Parameters
- Parameters refer to the relative intercepts of a crystal face on the three crystallographic axes.
- For example, if the intercepts are a, b, and c, then these are the parameters.
Indices
- Indices are whole numbers that represent the relationship of a crystal face to the crystallographic axes.
- They are derived from the parameters using the Miller system, by taking the reciprocals of the parameters.
Symbols
- Symbols provide a concise way to represent a crystal face using its indices.
Monoclinic System
- The Monoclinic system features three unequal crystallographic axes.
- One axis is inclined, while the other two are perpendicular.
- Common forms include pinacoid, domes, prisms, and pyramids.
Coal Formation
- Coal is a sedimentary rock formed from the transformation of vegetable matter through burial, compaction, and biochemical processes.
- Peat is the initial stage of coal formation, where vegetable structure is still visible.
- Lignite is a lower-rank coal, almost completely transformed from vegetable matter.
- Peat is a low-value fuel used domestically and in gas purification.
- Lignite is used as domestic fuel, for distillation, gasification, and in steam locomotives.
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Description
Explore the fascinating world of crystallographic forms and systems. This quiz covers different crystal face classifications, the isometric and hexagonal systems, and their unique characteristics. Test your knowledge on concepts like symmetry classes and axis relationships.
