corundum, synthetic corundum.7, gems

corundum, Montana.12, USA.12, gems

corundum, ruby, sapphire, Sri Lanka.12, geology.11, gems

corundum, quality.10, gems

corundum, history.1, India.12, gems, Indian lapidary

Sinkankas: This work presents translations of chapters 68–80 of the Sanskrit Garuḍa Purāṇa, which “elaborately describes the supernatural origin of gems and their mineralogical properties,” along with the Graha-cocāra Jyautiṣa, a text that “gives complete information on the astrological characteristics and effects of the principal gemstones” and “explains how auspicious gems help remove obstructions in various areas of life by appeasing planets that are having unfavorable effects.” The first thirteen chapters focus on planetary gemstones, offering summary translations of relevant Garuḍa Purāṇa passages concerning ruby, pearl, yellow sapphire, hessonite, emerald, diamond, cat’s-eye chrysoberyl, blue sapphire, coral, red garnet, jade (including jadeite), rock crystal, and bloodstone. Secondary planetary gemstones, or uparatnas, such as red spinel, moonstone, yellow topaz, citrine, hyacinth, peridot, tsavorite, green tourmaline, white zircon, turquoise, goshenite, amethyst, apatite cat’s-eye, blue spinel, tanzanite, lapis lazuli, and carnelian, are not directly traced to specific textual sources, and some—like tsavorite, goshenite, and tanzanite—were unknown to the ancients, suggesting these may have been included at the authors’ discretion. Each gemstone description includes its properties and modern sources, and although there is no bibliography, a valuable feature of the work is its inclusion of alternative Sanskrit names for the gemstones.

corundum, sapphire, Nigeria.12, gems

corundum, Thailand.12, Bo Ploi.12, gems

corundum, Pakistan.12, gems

gems, corundum, color.4, luminescence

The orange luminescence of α-Al₂O₃ under UV excitation is characterized by a 2.07-eV orange broadband emission that has not yet been elucidated. This emission is present in natural and synthetic crystals and powders, as well as in Be-treated samples. All orange-luminescent materials have low Fe concentration (mostly < 1000 ppm) with traces of divalent cations, mostly Mg, or Be in Be-diffused material (dozens of ppm). Mg²⁺, Mn²⁺, and Be²⁺ cations substitute for trivalent Al. To accommodate the charge deficit, several defects are created, including oxygen vacancies also called F centers. Indeed, our excitation spectra revealed the presence of several different F centers (F, F⁺, and clustered F₂, F₂⁺, F₂²⁺) in those samples. However, the thermal stability and the measured luminescence lifetimes do not match previously reported characteristics of isolated F centers. Based on our experiments, we suggest that a complex aggregate of two F centers (F₂²⁺) trapped at divalent cations is a major cause of this uncommon microsecond lifetime emission, even if a variety of other defects, including Cr³⁺, V³⁺, or interstitial Al³⁺, are present.

gems, corundum, treatments.4, beryllium diffusion

Accurate in situ analysis of beryllium (Be) is still a technical bottleneck in the fields of geoscience and materials science. In this study, we explored the analytical conditions of Be by using EPMA's state analysis of Be in different types of Be minerals (oxides, silicates, borates, and phosphates). Monte Carlo simulations suggested that a low accelerating voltage is conducive to the in situ analysis of Be. Optimized analytical conditions for Be minerals are obtained: 10 kV accelerating voltage, 50 to 100 nA beam current for hydrous Be minerals, greater than 100 nA beam current for anhydrous Be minerals, min beam size, PHA mode, and selecting the same Be minerals or similar Be minerals with the same structural environment of Be atoms as standard samples. Moreover, the analytical results of eleven types of Be minerals are close to the theoretical value or within the error range, showing that the in situ analysis of Be is completely feasible under the optimized analytical conditions. The low intensity of Be Kα under EPMA is most likely caused by the polyhedron structural environment, such as coordination, order and disorder, etc., and the influence of other chemical compositions (O, OH, and P) in Be minerals. The Fermi level decrease of EL in Be–O bonds results in the right shift of the X-ray peaks of Be. Overall, these experimental results and conclusions not only are helpful in revealing the mineralogical and geochemical properties of Be but also provide further insights into the distribution and metallogenic mechanism of Be in deposits.