5: Crystallography Last updated May 6, 2022 Save as PDF 4.3: The Chemical Classification of Gems and Minerals 5.1: Crystallography Page ID3199 gemologyGemology Project ( \newcommand{\kernel}{\mathrm{null}\,}\) 5.1: Crystallography5.2: Crystal Systems5.3: Form5.4: Habit5.5: Symmetry5.6: Twinning5.6.1: External Links