corundum, inclusions.5, Burma.12, Sri Lanka.12, Thailand.12, gems

Gübelin’s three-part study investigates the geographical identification of sapphires from Kashmir, Burma, Siam, and Ceylon, emphasizing microscopic inclusions as records of differing geological conditions. Reference specimens were obtained from selected dealers trading directly with the producing regions, while Ceylon’s fancy-colored sapphires supplied additional comparative material. The introductory discussion reviews characteristic colors, chemical differences, luminescence, refractive indices, and density, but cautions that these properties generally provide indications rather than certain determinations of origin. Comparative emission spectra of Burmese and Ceylon sapphires are interpreted in relation to their iron and titanium contents. Luminescence under cathode rays and ultraviolet radiation varies among the four sources, although exceptions and inconsistent responses limit its diagnostic value. Small differences in refractive index and specific gravity are likewise considered insufficient for confident identification alone. Microscopic examination forms the principal basis of the regional comparisons. Kashmir sapphires exhibit a characteristic haze that resolves under magnification into delicate veils of wavy, intersecting filaments arranged in hexagonal patterns. Gübelin distinguishes these from rutile needles, describing them instead as minute fissures or hollow tubes. Other Kashmir inclusions comprise thin films bordered by irregular networks of liquid-filled channels extending into individual droplets; their appearance changes as the stone is tilted. Burmese sapphires are characterized chiefly by short rutile needles densely distributed or grouped into patches, clouds, and zones. These follow the host’s crystallographic directions and intersect at 60° and 120° when viewed along the optic axis. Larger, well-formed rutile crystals and occasional curved liquid-filled cavities containing mobile gas bubbles are also described. Siamese sapphires are reported to lack rutile and instead contain broad, flat, loop-like fluid inclusions associated with opaque, approximately hexagonal features interpreted as resorbed crystals or negative crystals. Additional characteristics include brown material attributed to iron compounds, recrystallized inclusions in hexagonal arrangements, checkered twinning lamellae, and rows of script-like or arabesque fluid inclusions. Ceylon sapphires display a greater variety and generally less orderly distribution of inclusions. Their rutile needles are notably longer, sparser, and more widely spaced than those in Burmese material. Characteristic fluid feathers and flags comprise numerous tubular or wormlike cavities extending into isolated droplets, often with mobile gas bubbles; Gübelin identifies their liquid as carbon dioxide on the basis of his own investigations. He also describes scattered minute mineral inclusions, broad irregular fluid-filled tubes, and brown zircon crystals surrounded by pleochroic radiation halos. These zircons are regarded as particularly useful indicators of Ceylon origin, whereas accessory minerals occurring across several sources provide less decisive evidence. The study concludes that reliable interpretation requires extensive experience with numerous specimens and that photomicrographs offer a useful means of documenting the observed characteristics.