gems, quartz, rose quartz, inclusions, fiber inclusions, silk, dumortierite, analytical

Pink nanofibers were extracted from rose quartz samples collected from 29 pegmatitic and massive vein localities worldwide, with fiber widths ranging from 0.1 to 0.5 µm. Optical absorption spectra of both the nanofibers and the original rose quartz indicate that these nanofibrous inclusions are responsible for the coloration of massive rose quartz globally. Notably, such fibers are absent in the rare, euhedral variety of pink quartz. Redox and heating experiments revealed that the pink color arises from Fe-Ti intervalence charge transfer, which generates an optical absorption band at 500 nm. X-ray diffraction patterns and pleochroic behavior suggest that the inclusions are most similar to dumortierite; however, FTIR and Raman spectra show consistent deviations from standard dumortierite signatures, implying that the fibrous nanophase may not be dumortierite itself but a closely related mineral species.

gems, inclusions, beryl, emerald, Tanzania

Mineral and fluid inclusions were investigated in Tanzanian emeralds sampled in the Lake Manyara and Sumbawanga deposits. Microthermometry and Raman microprobe analyses were applied for this study. Primary and pseudosecondary H₂O–CO₂ inclusions, with numerous daughter solid phases, are common in the emeralds from the Lake Manyara deposit. Magnesite, Mg-calcite, aragonite, dolomite, calcite, nahcolite, quartz, and chrysoberyl were identified as trapped solids in fluid inclusions. Similar mineral inclusions were also found in the emeralds themselves. The composition of the trapped fluid present at emerald growth is estimated to be a carbonic-rich solution with chloride content of about 6 wt% NaCl equivalent. The P–T conditions of emerald growth are as follows: T = 370–470 °C and P = 3.0–7.0 kbar. Mineral inclusions of phenakite, euclase, bertrandite, and helvite are common in the emeralds of the Sumbawanga deposit. CO₂-rich inclusions with an aqueous phase (usually below the detection limit), and CaCl₂-rich inclusions with salinity of up to 17 wt% NaCl equivalent, are related to emerald growth. The trapping of fluid inclusions postdates the growth of mineral inclusions. The P–T conditions of emerald growth are as follows: T = 220–300 °C and P = 0.7–3.0 kbar.

corundum, phenomena, star sapphire, inclusions.5, gems

Black asteriated sapphires from Thailand that show distinct “silvery” white six-rayed stars are relatively well known in the gem trade, and they are also relatively common as compared to other colors of star sapphires. Occasionally, however, we see less typical asterism in this material. For example, some stars show 12 rays instead of six, or the star may appear “golden.”

corundum, Inclusions.5, Burma.12, gems

A large, slightly brownish green sapphire, reportedly from Myanmar, was recently seen in both the AGTA laboratory in New York and the GIA Gem Trade Laboratory in Carlsbad. The gem, an oval mixed cut that weighed 28.04 ct and measured 18.80 × 17.28 × 10.89 mm (figure 23), was brought to our attention by Joseph Krashes, of Krashes Dirnfeld, New York. It was interesting not only because of its size and color in relation to the stated locality, but also because of the inclusions it contained. The sapphire played host to a number of transparent to translucent brownish yellow inclusions (figure 24), a few of which had been exposed to the surface during faceting. When we examined some of the inclusions with higher magnification using a digital camera attached to a Raman microscope, we observed a crystal form that suggested that they were isometric, and no pleochroism was visible with polarized light. The slightly rounded surface of the inclusions suggested that dissolution might have occurred prior to their incorporation into the sapphire. The transparency and general condition of these inclusions and their immediate surroundings indicated that the host sapphire had not been subjected to high-temperature heat treatment—an important consideration in today’s sapphire market. Laser Raman microspectrometry of the inclusions at both laboratories identified them as pyrochlore. In the past, the pyrochlore inclusions we have encountered in sapphires have always been dark red to brownish red and observed in blue to blue-green sapphires (see, e.g., figure 25). This is the first time that either laboratory has identified brownish yellow pyrochlore inclusions in sapphire of any color.

corundum, color.4, gems

This retrospective study, based on samples analysed in the last twenty years, deals with heat treated rubies in respect of their content of foreign glassy fillings in fractures and subsequently healed fissures. Flux assisted heat treatment with borax, lithium tetraborate a.s.o. and additives of glass, quartz or melted natural inclusions may form a melt that spreads over the surface and is drawn in all fissures and cavities during heat treatment. The flux character of such melts produced during the treatment process enables a recrystallisation of former fissures. During cooling a small portion of (synthetic) ruby is formed that heals the former fissures. The flux may stay amorphous and glassy, but often precipitations of devitrification products are observed. The results of treatment under flux conditions are not only healing structures similar to natural ,,fingerprints“, but also residual portions of the flux material (commonly called ,,glass“) which is kept in fine droplets, channels, or thin films, up to surface reaching larger cavities. The different amounts of foreign residues in a ruby lead to the request of a quality scale. When residues are addressed in test reports, a scale with three levels has been widely accepted (e.g. minor, moderate, significant/prominent).

corundum, sources.12, Sri Lanka.12, gems

Gem production in Sri Lanka has declined in recent years as the traditional alluvial (secondary) deposits have been depleted and new alluvial deposits become increasingly difficult to find. Yet this trend may be reversed as new in-situ (primary) gem deposits are being discovered with the help of modern satellite technology in areas not previously known to have gem occurrences. These primary deposits reportedly are hosted by skarns (carbonate rocks, such as limestone, affected by contact metamorphism accompanied by the introduction of additional elements). One of the new areas, near Kataragama in the extreme southeastern part of the island, is mainly producing blue sapphires, some of fine quality, along with other gems (including yellow and orange-pink sapphire, garnet, and red spinel). Although well-formed crystals have been found, they typically contain abundant inclusions and cracks. Both traditional hand methods and mechanized mining are being used, with careful attention to environmental matters.JEC

corundum, geology.11, Australia.12, Laos.12, gems

Australia and Southeast Asia have been the sources of large amounts of sapphire associated with basaltic rocks. It is universally accepted by geologists that the sapphires did not crystallize directly from the basalts; rather, the basalts merely were the transporting mechanism that brought the sapphires to the surface. Over the past decade, two types of sapphires associated with basalts from these areas have been recognized, based on variations in their trace-element contents. Dr. F. L. Sutherland of the Australian Museum, Sydney, postulated that sapphires with a Cr₂O₃/Ga₂O₃ ratio less than 1 crystallized from a magma, whereas those with a Cr₂O₃/Ga₂O₃ ratio greater than 1 formed by a metamorphic process. To help prove this hypothesis, Dr. Sutherland and co-workers have obtained information on the age of sapphires from both inferred origins. Sapphires of such different geological origins should show discrete differences in their crystallization ages. Syngenetic zircon inclusions (figure 7) in both types of sapphire were dated by uranium-lead isotope methods. Vastly different ages (ranging from 2.8 to 900 million years) were obtained in a study of Australian sapphires of both types, from Queensland and New South Wales. The younger ages correspond to sapphires with a magmatic origin, while the older sapphires have trace-element ratios that indicate a metamorphic origin. The youngest ages obtained so far (1.1–1.5 million years) were found in magmatic-type sapphires from Laos.

gems, jade, jadeite jade, magma genesis, fluid inclusion, primary texture, secondary texture, pyroxene jade, Burma, Myanmar

Through the field survey of Myanmar jadeite jade, the microscope observation of a lot of jadeite jade thin sections and fluid inclusions and more than one hundred EPMA analysis, the hypothesis of jadeite jade genesis is reviewed, the geological characteristics of jadeite jade in the world is summarized, the types and characteristics of fluid inclusions are described, the relationship between jadeite jade texture and its genesis is discussed, a new viewpoint—magma genesis of jadeite jade—is put forward, and the p t condition under which jadeite jade crystallized is analyzed. The magma from which jadeite jade crystallized is hydrous jadeitic silica melt which may come from mantle. The crystal condition is p >1.5 GPa, t=650~800℃. This hypothesis of magma genesis put forward before.

jade, jadeite, fei cui, Burma, inclusions, gems

Numerous liquid–gas and liquid–gas–solid inclusions have been identified in jadeitites from the Pharkant region of northwestern Myanmar, and their characteristics, geological context, and the occurrence of porphyroclastic jadeite containing such inclusions have been thoroughly described. Raman spectroscopic analysis revealed that the fluid inclusions are composed of H₂O + CH₄ in the liquid–gas phase, and jadeite as the solid (daughter) phase. These findings suggest that the Pharkant jadeitites crystallized from a jadeitic melt bearing H₂O and CH₄, potentially of mantle origin. The inferred pressure–temperature conditions for their crystallization are estimated to be above 650 °C and greater than 1.5 GPa..

gems, beryl, emerald, Egypt, geology, chemistry

Mineralogical, geochemical and fluid inclusion studies reveal two favorable environments for the localisation of beryl mineralisations in the Precambrian rocks of Egypt: (1) emerald–schist; and (2) beryl-specialised granitoid associations. Emerald occurs within the mica schists and is typically confined to the Nugrus major shear zone. However, beryl associated with granitoids occurs in pegmatite veins, greisen bodies, and cassiterite–quartz veins cutting the granites and the exocontacts of the volcanosedimentary country rocks. Compositionally, emerald is of octahedral type and its cell edge is lengthened along the a-axis, while beryl associated with granitoids is normal in composition and structural constants. Emerald is thought to be formed as the result of epitactic nucleation of Be, Al and alkali-rich solutions on the mica of the schist country rocks. Fluid inclusion studies show that the solutions are saline (8–22 wt% NaCl equiv.) and the reactions proceeded in the temperature range 260–382 °C. On the other hand, aqueous inclusions in beryl associated with granitoids show the following sequence of formation with decreasing temperatures and salinities: beryl pegmatite (320–480 °C and 7–16 wt% NaCl equiv.) → greisen bodies (190–400 °C and 4–7 wt% NaCl equiv.) → cassiterite–quartz veins (190–380 °C and 2–4 wt% NaCl equiv.). This study suggests that factors such as the chemistry of the Be-bearing fluids (rather than that of the bulk host schists) and syn-tectonic intrusions of leucogranites and pegmatites (Be-deriving sources) along major ductile shear zones are the important factors controlling emerald formation. However, the endogreisens and exogreisens are the most important targets characterising the metasomatically- and magmatically-specialised, Be-granitoids, respectively. The aqueous inclusions examined in greisen beryls of metasomatised granites show a shorter range of homogenisation temperatures (260–390 °C) and salinities (4.8–7 wt% NaCl equiv.) as compared to those of magmatically-specialised granitoids (190–400 °C and 4–7 wt% NaCl equiv.). This phenomenon can be partly attributed to the late development of the fracture system during the crystallisation history of the metasomatised granites, where little or no contribution from meteoric waters occurred.