New data on painite

A crystal of painite discovered in 1979 in a parcel of rough gem spinel from Burma represents the third known crystal of the species. This crystal is similar to the type crystal in most respects. Chemical analyses of both the new crystal and the type crystal confirmed the essential constituents reported by Moore and Araki (1976) and showed in addition the presence of trace amounts of Fe, Cr, V, Ti, Na, and Hf. Optical absorption spectra suggest that the red colour of painite is caused principally by Cr^(3+) and V^(3+)

Upper Stage Engine Composite Nozzle Extensions

Carbon-carbon (C-C) composite nozzle extensions are of interest for use on a variety of launch vehicle upper stage engines and in-space propulsion systems. The C-C nozzle extension technology and test capabilities being developed are intended to support National Aeronautics and Space Administration (NASA) and United States Air Force (USAF) requirements, as well as broader industry needs. Recent and on-going efforts at the Marshall Space Flight Center (MSFC) are aimed at both (a) further developing the technology and databases for nozzle extensions fabricated from specific CC materials, and (b) developing and demonstrating low-cost capabilities for testing composite nozzle extensions. At present, materials development work is concentrating on developing a database for lyocell-based C-C that can be used for upper stage engine nozzle extension design, modeling, and analysis efforts. Lyocell-based C-C behaves in a manner similar to rayon-based CC, but does not have the environmental issues associated with the use of rayon. Future work will also further investigate technology and database gaps and needs for more-established polyacrylonitrile- (PAN-) based C-C's. As a low-cost means of being able to rapidly test and screen nozzle extension materials and structures, MSFC has recently established and demonstrated a test rig at MSFC's Test Stand (TS) 115 for testing subscale nozzle extensions with 3.5-inch inside diameters at the attachment plane. Test durations of up to 120 seconds have been demonstrated using oxygen/hydrogen propellants. Other propellant combinations, including the use of hydrocarbon fuels, can be used if desired. Another test capability being developed will allow the testing of larger nozzle extensions (13.5- inch inside diameters at the attachment plane) in environments more similar to those of actual oxygen/hydrogen upper stage engines. Two C-C nozzle extensions (one lyocell-based, one PAN-based) have been fabricated for testing with the larger-scale facility

Green orthoclase feldspar from Vietnam

In July 2005, these contributors received some interesting transparent "emerald" green samples that were reported to be amazonite from a new find in Vietnam. Five faceted stones were loaned and several pieces of rough were donated to GIA by Bill Larson (Pala International, Fallbrook, California). According to his supplier, Son T. Ta (I.T.C. International Trade Center, Ho Chi Minh City, Vietnam), they were mined from a pegmatite near Minh Tien, about 15 km south of Luc Yen in Yen Bai Province. This area is also known to produce transparent green fluorite, which when cobbed is similar in appearance to gem-quality orthoclase

Origin of color in cuprian elbaite from São José de Batalha, Paraíba, Brazil

Gem-quality elbaite from Paraíba, Brazil, containing up to 1.4 wt% Cu has been characterized using optical spectroscopy and crystal chemistry. The optical absorption spectra of Cu^(2+) in these tourmalines consist of two bands with maxima in the 695- to 940-nm region that are more intense in the E ⊥ c direction. The vivid yellowish green to bluegreen colors of these elbaite samples arise primarily from Cu^(2+) and are modified to violetblue and violet hues by increasing absorptions from Mn^(3+)

New data on Lotharmeyerite

The new species lotharmeyerite from the Ojuela mine, Mapimi, Durango, Mexico was recently described by Dunn (1983). Unfortunately, the very small crystals in drusy growths which that author had at his disposal did not permit the determination of a number of important characteristics. The availability of larger, individual crystals from the same locality now makes possible a more complete description of the species

Gem-Quality Cuprian-Elbaite Tourmalines from São José Da Batalha, Paraíba, Brazil

Unusually vivid tourmalines from the state of Paraíba, in northeastern Brazil, have attracted great interest since they first appeared on the international gem market in 1989. This article describes what is known of the locality at this time, but focuses on the most striking characteristic of these gem tourmalines: the unusual colors in which they occur. Quantitative chemical analyses revealed that these elbaite tourmalines contain surprisingly high concentrations of copper, up to 1.92 wt.% Cu (or 2.38 wt.% CuO). Their colors are due to Cu^(2+) or a combination of Cu^(2+), Mn^(3+), and other causes. Some colors can be produced by heat treatment, but most also occur naturally

Developments in Gemstone Analysis Techniques and Instrumentation During the 2000s

The first decade of the 2000s continued the trend of using more powerful analytical instruments to solve gem identification problems. Advances in gem treatment and synthesis technology, and the discovery of new gem sources, led to urgent needs in gem identification. These, in turn, led to the adaptation of newer scientific instruments to gemology. The past decade witnessed the widespread use of chemical microanalysis techniques such as LA-ICP-MS and LIBS, luminescence spectroscopy (particularly photoluminescence), real-time fluorescence and X-ray imaging, and portable spectrometers, as well as the introduction of nanoscale analysis. Innovations in laser mapping and computer modeling of diamond rough and faceted stone appearance changed the way gemstones are cut and the manner in which they are graded by gem laboratories