corundum, ruby, sapphire, inclusions.5, Kashmir.11, India.12, gems

Gübelin reviews the diagnostic value of gemstone inclusions and their significance for understanding mineral formation. Improved dark-field binocular microscopy permits examination of inclusions throughout a faceted stone, revealing characteristic differences in their composition, form, orientation, and distribution. Inclusions are classified both by their timing relative to host-crystal growth and as solid, liquid, or gaseous components. Examples from diamond, corundum, beryl, garnet, tourmaline, spinel, moonstone, and fluorite illustrate their use in gemstone identification and, in some cases, determining geographical origin. Particular attention is given to locality-specific inclusion assemblages in rubies and sapphires, three-phase inclusions in emeralds, and characteristic mineral inclusions in garnets. The paper emphasizes that diagnostic value frequently resides in the overall inclusion pattern and its relationship to crystal structure, rather than in an isolated inclusion. Five plates illustrate representative features. Gübelin advocates closer collaboration between gemmology and mineralogy to advance both practical identification and interpretation of crystal growth.