1 Introduction.- 1.1 Occurrence and Abundance of Silicon.- 1.2 Technical Importance of Silicon.- 1.3 Diversity of Silicon Compounds.- 2 Methods to Describe the Atomic Structure of Silicates.- 2.1 Model Representations of Silicate Structures.- 2.2 Treatment of Tetrahedrally Coordinated Cations in Silicates.- 3 Chemical Bonds in Silicates.- 3.1 The Silicon - Oxygen Bond.- 3.2 The Cation - Oxygen Bond, M-O, and Its Influence on the Si-O Bond.- 4 Crystal Chemical Classification of Silicate Anions.- 4.1 General Principles of the Classification.- 4.2 Parameters Used in the Crystal Chemical Classification of Silicate Anions.- 4.3 The Crystal Chemical System of Silicate Anions.- 4.4 Periodic Character of the Crystal Chemical Classification of Silicate Anions.- 5 Nomenclature and Structural Formulae of Silicate Anions and Silicates.- 5.1 Nomenclature.- 5.2 Structural Formulae.- 6 Crystal Chemical Classification of Silicates: General Part.- 6.1 Mixed-Anion Silicates.- 6.2 The Crystal Chemical System of Silicates.- 6.3 Further Subdivision of Silicates.- 6.4 Silicate Classification Procedure.- 6.5 Shortcomings of the Crystal Chemical Classification.- 7 Crystal Chemical Classification of Silicates: Special Part.- 7.1 Silicon Compounds with [SiO6] Octahedra (Hexaoxosilicates).- 7.2 Silicates Containing [SiO4] Tetrahedra (Tetraoxosilicates).- 7.3 Mixed-Anion Silicates.- 7.4 Estimated Frequency Distribution of Silicate Species.- 8 Other Classifications of Silicates.- 8.1 Early Classifications of Silicates.- 8.2 Rostov's Classification of Silicates.- 8.3 Zoltai's Classification of Silicates.- 8.4 Geometrical Classification of Tectosilicates.- 8.5 Silicate Classification Based on Non-Silicon Cation - Oxygen Polyhedra.- 9 General Rules for Silicate Anion Topology.- 10 Influenceof Non-Tetrahedral Cation Properties on the Structure of Silicate Anions.- 10.1 Influence of Cation Properties on the Conformation of Unbranched Single Chain Anions.- 10.2 Influence of Cation Properties on the Shape of Unbranched Multiple Chain Anions.- 10.3 Influence of Cation Properties on the Shape of Branched Silicate Anions.- 10.4 Influence of Cation Properties on the Formation of Cyclic Silicate Anions.- 10.5 Influence of Cation Properties on the Shape of Single Layer Silicate Anions.- 10.6 Influence of Cation Properties on the Shape of Double Layer Silicate Anions.- 10.7 Influence of Cation Properties on the Shape of Silicate Frameworks.- 11 Conclusion.- 11.1 Correlation Between Classification Parameters and Cation Properties.- 11.2 Influence of Cation Radius on the Structure of Silicates.- 11.3 Characteristics of the Crystal Chemical Classification of Silicates.- References.- Appendices I-III.- Substance Index.- Formula Index.