علم البلورات - الفصل الأول

Course Information

• Course: Mineralogy
• Semester: First
• Topic: Crystallography
• Academic Year: 2025-2024
• Lecturer: Shleer Burhan
• Date: 26/11/2024

Introduction to Crystallography

• Crystallography studies the arrangement of atoms in crystalline solids.
• It is fundamental to understanding the physical properties of minerals.

Basic Building Blocks

• Solid Universe: Earth, Moon, Planets, and Meteorites
• Rocks: Igneous, Metamorphic, Sedimentary
• Gemstone: Diamond
• Earth History: Zircon

Course Description

• First Semester: Crystallography
• Second Semester: Mineralogy

Course Overview

• Crystallography: Determining the arrangement of atoms in crystalline solids.
• Mineralogy: The study of naturally occurring crystalline substances.

Course Objectives

• Identifying minerals
• Understanding mineral properties
• Distinguishing between minerals
• Exploring mineral genesis and origin
• Recognizing the most abundant mineral groups
• Appreciating the significance of minerals

Exam Schedule

• 1st Exam
• 2nd Exam

Topics to Cover (2nd Exam)

• Introduction
• Basics of Crystallography
• Polyhedrons & crystallographic axes
• Crystal System
• Symmetry elements
• Crystal Form
• Axial Ratio & Face Intercepts
• Miller Indices

Basics of Crystallography

• Definition: A scientific branch that examines the structural arrangement, internal geometry, and physical properties of crystalline materials.
• Characteristics: Focuses on defining and describing crystals.

Why Study Crystallography?

• Crucial for mineral identification.
• Enables understanding how minerals form.

Matter

• Structure: Crystalline, Non-Crystalline
• Composition: Ions (Cations vs. Anions), Chemical bonds
• States: Gas, Liquid, Solid

Mineral Criteria

• Solid: Stable state of matter
• Natural: Formed through natural processes.
• Inorganic: Not derived from living organisms.
• Chemical formula: Unique chemical composition.
• Stable at 25°C: Existence under standard conditions.
• Specific Properties: Specific characteristics distinctive to the mineral (e.g. hardness or density)

Crystallography (Detail)

• Definition: Study of crystals.
• Structural Crystallography: Study of the interior of crystals.
• Geometrical Crystallography: Study of the external shape of crystals.

Crystal Parts

• Faces: Surfaces bounding the crystal.
• Edges: Intersections of two faces.
• Solid Angle: Intersection of 3 or more faces.
• Interfacial Angle: Angle between two faces.

How to Measure Interfacial Angles

• Contact Goniometer
• Reflection Goniometer

Polyhedra

• Definition: Solids in three dimensions composed of faces, edges, and vertices.
• Types: Tetrahedron, Octahedron, Cube, Dodecahedron, Icosahedron

Symmetry

• Parts facing each other or around an axis have a symmetrical relationship.

Crystal Axes

• Define the crystal by lengths and angles.
• Three main axes (a, b, c) and three interaxial angles (alpha, beta, gamma).

Chemical Bonds

• Ionic Bonds: Electrostatic attraction between oppositely charged ions.
• Covalent Bonds: Sharing of electron pairs between atoms.
• Metallic Bonds: Attraction between conduction electrons and positively charged metal ions.

Coordination Number

• Number of ions/atoms surrounding a central ion/atom.

Relative size of Ions (Cation/Anion)

• Cation/Anion size ratio influences crystal structure.
• The relative sizes affect the coordination number.

Crystalline vs. Amorphous Solids

• Crystalline: Regular, periodic atomic arrangement, anisotropic properties, sharp melting points.
• Amorphous: Lacking long-range order, isotropic, no well-defined melting point.

How Crystals Form (Example: Salt)

• Dissolving salt in water.
• Evaporation of water leaves behind salt crystals.

يتناول هذا الاختبار موضوع علم البلورات في الفصل الأول من دورة المعادن. يركز على ترتيب الذرات في المواد البلورية وخصائص المعادن المختلفة. يعد هذا الموضوع أساسياً لفهم الخصائص الفيزيائية للمعادن.