gems, Red Sea, Egypt, emerald, ancient gems, ancient trade, glyptic, archaeology, archaeogemology, trade routes, Roman

Not since the Ptolemaic-Roman-Byzantine era (late 4th century B.C. to 7th century A.D.) have the Eastern Desert and Red Sea coast of Egypt witnessed the activity now taking place, as tourism and settlements for Egypt’s burgeoning population encroach into once sparsely settled areas. During the Ptolemaic, Roman, and Byzantine periods, a healthy trade between the Mediterranean region, South Arabia, East Africa, and South Asia traversed the Eastern Desert and the Red Sea (Fig. 1). These trade routes fell into disuse with the decline of the Roman Empire and virtually disappeared with the discovery of the sea route around the Horn of Africa in the late 15th century. The opening of the Suez Canal in 1869 somewhat revived commerce in this area, but for most of the period between the 7th and the 19th century, the Eastern Desert lay nearly abandoned. Evidence of scores of ancient sites remained unrecorded until now.

corundum, spinel, Tajikistan.12, balas ruby, gems

Large spinel from Tajikistan. Spinel is another gem material being recovered from this former Soviet republic in Central Asia. We know of one particularly exceptional stone, a 532-ct piece of rough spinel, that was fashioned into a number of gems. The largest of these gems weighed 146.43ct and was named the Katherina" by the purchaser of the rough, the Netherlands-based ACT International (see "Spectacular Spinel," by P. Bancroft, Lapidary loiunal, February 1990, p. 25). The Katherina was subsequently recut to 123.14ct (E. Caplan, pers. comm., 1995) and the refashioned stone loaned to GIA for examination. Although recut, it retained its basic step-cut cushion shape (figure 16).The stone exhibited properties consistent with natural spinel from other localities. Described as "virtually flawless" in the Lapidary lournal article, the stone revealed a small plane of what appeared to be octahedral negative crystals near the culet when examined with magnification. These substantiate the stone's natural origin. EDXRF chemical analysis by GIA Research showed only a tiny amount of zinc (Zn), which is consistent with Zn concentrations that have been documented in other spinels from this locality."

corundum, geology.11, Australia.12, gems

corundum, properties.3, Burma.12, Möng Hsu, gems

The article Update on Diffusion-Treated Corundum: Red and Other Colors" (S. F. McClure et al., Gems d Gemology, Spring 1993, pp. 16-28) focused on treated stones in purplish pink, reddish purple to purplish red, and orangy red hues. One feature documented in many of these sample stones, in contrast to documented blue diffusion-treated sapphires, was the presence of unusually high refractive indices. The authors speculated that this was due to the high chromium content in the diffused surface layer, and they made reference to a report in the literature mentioning high R.I. readings from high-chromium-content rubies and orange sapphires from Malawi."

jadeite, fei cui, b-jade, gems, gem treatments, bleached jade, impregnated jade

X-ray photoelectron spectroscopy (XPS) is investigated as a non-destructive method for identifying wax and polymer in bleached and impregnated fei cui and as a complement to infrared absorption spectroscopy. Sixteen specimens from Myanmar were examined, comprising four rough specimens, five naturally coloured polished specimens and seven bleached, wax- or polymer-impregnated polished cabochons. Preliminary testing included refractive index, immersion in di-iodomethane, visible absorption spectroscopy, ultraviolet fluorescence and Fourier-transform infrared spectroscopy. Refractive indices, immersion behaviour and visible absorption features did not reliably distinguish treated from untreated material; ultraviolet fluorescence provided indications of treatment in some specimens but was absent in others. Infrared spectra differentiated weak wax absorptions associated with conventional polishing from the much stronger absorptions of wax-impregnated specimens, while multiple strong bands between 2800 and 3100 cm⁻¹ identified polymer impregnation. XPS measurements, made after cleaning the surfaces with propanol, determined surface elemental composition and carbon bonding characteristics through survey scans and high-resolution carbon spectra. Untreated, unwaxed specimens showed the principal elements expected for jadeite, together with minor surface carbon and calcium. Their carbon-to-sodium signal ratio was approximately 2.5, compared with approximately 12 for wax-polished specimens, 11 for wax-impregnated specimens and 35 for polymer-impregnated specimens. The substantially greater carbon signal in the polymer-treated group distinguished it from the wax-bearing groups. Analysis of the carbon peak components provided further discrimination: wax-bearing material showed aliphatic, ether and ester contributions, whereas the polymer-impregnated specimens showed aliphatic, aromatic or phenyl, carbonyl and ester contributions. Ether carbon was characteristic of the wax examined, while phenyl and carbonyl components characterised the polymer used in these specimens. A significant limitation is that XPS samples only the outermost surface, to a depth of approximately 5 nm, and therefore could not distinguish conventional wax polishing from wax impregnation on the basis of their similar surface compositions. Infrared absorption measurements remained necessary to assess the greater bulk wax content associated with impregnation. The study demonstrates the complementary roles of surface-sensitive XPS and bulk-sensitive infrared spectroscopy: XPS identifies surface fillers and their chemical characteristics, while infrared spectroscopy helps establish their abundance within the material. Together, the methods provide stronger evidence for identifying treated fei cui than routine gemmological observations alone.

corundum, Burma.12, USA.12, North Carolina.12, gems

More on Czochralski “pulled” synthetic sapphires. The Spring 1993 and Summer 1994 Gem News sections contain entries on Czochralski-pulled synthetic sapphires seen at the 1993 and 1994 Tucson shows. All the colors mentioned in those entries—including blue—were again seen at the 1995 shows. According to one vendor of this material, Gerry Manning of Manning International, New York, the pulled synthetic blue sapphire crystals are unevenly colored. The first-grown portions of the rod-shaped crystals are lightest in color; the rods become increasingly darker toward the opposite end (the last part to crystallize). The color zoning described by Mr. Manning differs from that seen in split boules of flame-fusion synthetic blue sapphire. There, the color is typically lightest in the center and progressively darker toward the periphery. Mr. Manning provided two faceted blue specimens (figure 20) for gemological characterization. Properties determined were: R.I. – nₚ = 1.760; nₒ = 1.768; birefringence ≈ 0.008; S.G. (determined hydrostatically) ≈ 4.0 to 4.01. Both specimens were inert to long-wave UV and fluoresced a weak, chalky bluish green to short-wave UV. All these properties are similar to those of flame-fusion synthetic blue sapphires. We also noted weak red fluorescence to intense transmitted light from a fiber-optic light source, and the samples appeared faintly pink through the Chelsea color filter. These latter two reactions have been noted in some violetish blue flame-fusion synthetic sapphires that contain traces of chromium, as well as in some natural blue-to-violet sapphires from Sri Lanka that also contain traces of chromium. Magnification revealed minute gas bubbles in both samples. Unlike flame-fusion synthetic sapphires, however, although the color of our samples did not appear totally uniform, we could not resolve curved color banding using diffused transmitted light and magnification. Only when this lighting technique was combined with immersion of the samples in methylene iodide could we see wide, slightly curved blue banding, which is proof of synthesis.

corundum, Tanzania.12, gems

corundum, treatments.6, gems

corundum, synthetic corundum.7, gems

corundum, Burundi.12, Cambodia.12, Sierra Leone.12, gems