1. Introduction.- 2. General Description of the Zeolites.- 2.1 Grouping of Zeolites.- 2.2 Chemical Classification of Zeolites.- 2.3 Secondary Building Units.- 2.4 Channel, Cage and Cavity Systems.- 2.5 Zeolitic Water Related to Cations.- 3. Hydrothermal Synthesis under Pressure.- 3.1 Physical Chemistry of Hydrothermal Synthesis Under Pressure.- 3.2 Experimental.- 4. Zeolite Identification by the Stereo-Comparator Method.- 4.1 Imaging Technique with the Scanning Electron Microscope.- 4.2 Image Evaluation with the Stereo-Comparator.- 4.3 The Calculation of x, y, z from Px and Py.- 4.4 Crystal Indexing.- 5.The Zeolite Minerals.- 5.1 Zeolites with 4=1 Chains.- 5.2 Zeolites with Single Connected 4-Ring Chains.- 5.3 Zeolites with Double Connected 4-Ring Chains.- 5.4 Zeolites with 6-Rings.- 5.5 Zeolites with 5-1 Building Units.- 5.6 Zeolites with 4-4=1 Building Units.- 6. Concluding Remarks.- 7. Acknowledgment.- 8. Index.- 9. References.