corundum, ruby, Nepal.12, inclusions.5, geology.11, gems

Ruby reportedly originating from a new occurrence in Nepal is characterized through examination of two cut stones, a large prismatic crystal in a carbonate-rich matrix, and corundum-bearing mica schist. The precise locality was undisclosed, and a possible connection with previously reported material from Taplejung remained unconfirmed. Initial examination of a 7.90 ct cabochon and a 2.17 ct faceted stone raised identification difficulties because curved, twisted feather-like inclusions resembled features observed in several synthetic rubies. Subsequent study of rough specimens demonstrated comparable fluid-bearing fractures and undulating films in natural corundum. Straight blue sapphire bands occur within the rubies, and a section through the prismatic crystal reveals a strongly coloured ruby core surrounded by paler red zones and sharply defined blue bands with growth lines meeting at 120°. Accurate refractive indices measured on the polished section are 1.760–1.768. Specific gravities of the two cut stones are 3.99 and 3.98, while the inclusion-rich crystal section has a lower value of 3.79, attributed to abundant margarite. Ultraviolet–visible spectroscopy of differently coloured zones yields predominantly ruby-type absorption patterns, with additional absorption associated with the blue regions. An ultraviolet absorption minimum at 361 nm supports natural origin under the comparative method employed. Electron-microprobe analyses detect up to 0.32 wt% Cr₂O₃ and 0.30 wt% TiO₂, although titanium content does not correlate consistently with blue colour intensity; iron remains below the analytical detection limit of approximately 0.2 wt% oxide. Identified inclusions and associated minerals include margarite, muscovite, zoisite, epidote, rutile and apatite, with some apparently black apatite owing its colour to graphite. The prismatic crystal’s matrix consists chiefly of calcite, dolomite and margarite, whereas the schist is dominated by phlogopite with apatite, graphite and corundum. Ruby fluoresces red to pink, more strongly under long-wave ultraviolet radiation, while margarite displays conspicuous greenish-white fluorescence and sapphire zones fluoresce less strongly. Margarite mantling and intersecting corundum is tentatively interpreted as partial replacement following changes in metamorphic conditions. The mineral assemblage resembles carbonate-associated ruby occurrences at Mogok and in Pakistan’s Hunza Valley. The study emphasizes both these geological affinities and the identification risks posed by natural inclusions that resemble those of synthetic ruby.