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Questions and Answers
What is the definition of a crystal?
What is the definition of a crystal?
A natural solid body, with a regular atomic arrangement, a certain chemical composition, and bounded by plane surfaces.
What is crystallography?
What is crystallography?
A branch of science focused on the geometry of internal structure and physical properties of crystalline materials.
Which of these is NOT a characteristic of a mineral?
Which of these is NOT a characteristic of a mineral?
What are the two main branches of crystallography?
What are the two main branches of crystallography?
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What is the difference between crystalline solids and amorphous solids?
What is the difference between crystalline solids and amorphous solids?
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What is the purpose of using a goniometer?
What is the purpose of using a goniometer?
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What are the three key components of a polyhedron?
What are the three key components of a polyhedron?
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What is a form in crystallography?
What is a form in crystallography?
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Study Notes
Lecture 1 - Introduction to Crystallography
- Topic: Introduction to Crystallography, lecture given on 26/11/2024 by Assistant lect. Shleer Burhan
- Course: Mineralogy: Mineral Science 2025-2024
- First Semester: Crystallography
- Second Semester: Mineralogy
- Course Description: Basic building of solid universe (Earth, Moon, Planets, meteorites), Human developments (railway, cars, electricity, communication, building, agriculture), Rocks (igneous, metamorphic, sedimentary), National economic (strategic minerals, Gold, Silver, PGE, REE, Cu, Fe, Uranium), Gemstone (Diamond), Earth history and ages (Zircon)
- Course Overview: Crystallography is the science of determining the arrangement of atoms in crystalline solids. Mineralogy is the study of naturally occurring crystalline substances.
Course Objective
- What is a crystal?
- What are minerals, and how are they different from rocks?
- What are the major parts of crystals?
- What is the crystal symmetry and crystal form?
- What is the classification of crystals according to system?
- What is the basic of a mineral?
- What are some physical and chemical properties of minerals?
- How can these properties be used to distinguish one mineral from another?
- What is the genesis and origin of minerals?
- What is the most abundant mineral group?
- What are the important properties of minerals?
Exams
- 1st Exam: Lec 1: Introduction, Lec 2: Basics of Crystallography, Lec 3: Polyhedron & Crystallographic axes, Lec 4: The crystal system, Lec 5: Elements of symmetry, Lec 6: Crystal Form, Lec 7: Axial Ratio & Faces intercepts, Lec 10: Crystal Projection, Lec 9: Crystal Habit, Lec 8: Miller Indices, Lec 11: Crystal Lattice, Lec 12: The 14 Bravais Lattices, Lec 13: The 32 Point Groups (Crystal Classes)
- 2nd Exam: All topics from the first semester covered in the lecture series
Basic of Crystallography
- Definition: A branch of science that studies the geometry, internal structure and physical properties of crystalline materials.
- Crystal: A natural solid with a regular atomic arrangement and specific chemical composition, bounded by plane surfaces.
- Crystallization: The process of forming a crystalline structure from a fluid or dissolved materials (rarely, directly from gas).
Chemical Composition
- Cation: A positively charged ion (P>E)
- Anion: A negatively charged ion (E>P)
- Atoms combine due to the electrostatic attraction (bonds).
- Charges (loss or gain of electrons) are characteristics of an atom.
Bonds
- Types of chemical bonds include ionic, covalent, and metallic.
Common Elements and Minerals
- Eight main elements are the majority of Earth's crust and mantle (oxygen, silicon, aluminum, iron, calcium, sodium, potassium, magnesium).
- The relative amount of each element is given in percentages.
Coordination Number
- The number of ions or atoms surrounding an atom or ion in a crystalline structure.
- Relative size of cation and anion (Rx/Rz) determines the coordination number. (Hexagonal closest packing, cubic closest packing)
Crystal Solids vs. Amorphous Solids
- Crystalline solids have regular, periodic atomic arrangements; exhibit anisotropic properties (properties depend on direction), sharp melting points
- Amorphous solids do not have a regular arrangement; exhibit isotropic properties (properties are same in every direction), lack sharp melting points
Crystal Parts
- Faces: Plane surfaces bounding a crystal.
- Edge: Intersection of two adjacent faces.
- Solid Angle: Point where three or more adjacent faces meet.
- Interfacial Angle: Angle between two adjacent faces, usually measured using a goniometer.
- Crystal symmetry: Similar parts of the crystal facing each other (or around an axis).
- Crystal form/habit: Physical shape or appearance of a crystal.
- Crystal axes: Three axes that define a crystal system.
How to Measure Interfacial Angle
- Contact Goniometer: A tool used to measure interfacial angles.
- Reflection Goniometer
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Description
This quiz covers the foundational concepts of crystallography as introduced in Lecture 1 of the Mineralogy course for the academic year 2025-2024. It explores key topics such as crystal structures, minerals, symmetry, and the significance of crystals in the natural world and human development.
