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Abstract: In our paper we supposed that the Paleozoic ages of the Bixiling eclogitic garnets by 40Ar/39Ar crushing in vacuo were related to the UHP metamorphism. Zhao and Gao [Zhao Z.-F. and Gao T.-S. (2007) Comment on “Paleozoic ages and excess 40Ar in garnets from the Bixiling eclogite in Dabieshan, China:Newinsights from 40Ar/39Ar dating by stepwise crushing” by Qiu and Wijbrans (2006). Geochim. Cosmochim. Acta 71(24), 6046–6050] dispute our conclusions and re-interpret them as “the age of garnet growth by low-T/HP blueschist/eclogite-facies metamorphism of the UHP eclogite precursor during arc-continent collision in the early Paleozoic” without presenting any new petrological evidence. Based on our present understanding of 40Ar/39Ar crushing technique and petrological observations, we do not agree with their re-interpretation and still prefer our original interpretation. [Copyright &y& Elsevier]

The paper described the shock-wave synthesis of high-pressure high-temperature mineral MgAl2O4 with the parameter a = 8.085(3) Å and the Laves phase MgCu2 with a = 7.076(2) Å from a mixture of MgO and aluminum powder placed into a copper insert inside a steel conservation ampoule. Spinel MgAl2O4 with a smaller lattice parameter a = 8.0798 Å has been formed in an aluminum insert cup. [ABSTRACT FROM AUTHOR]

Discussed in this paper are several theoretical and computational approaches that have been used to better understand the fracture of both single-crystal and polycrystalline diamond at the atomic level. The studies, which include first principles calculations, analytic models and molecular simulations, have been chosen to illustrate the different ways in which this problem has been approached, the conclusions and their reliability that have been reached by these methods, and how these theory and modelling methods can be effectively used together. [ABSTRACT FROM AUTHOR]

The article discusses the examination of a turquoise bead necklace by the Gemological Institute of America (GIA)'s Carlsbad laboratory in California and adds the research paper "Gemstone enhancement and its detection in the 2000s" by researcher S.F. McClure and colleagues.

ABSTRACT The rarity of jade as well as its hardness, durability, and sacred color gave it a value incomparable to other materials in Mesoamerica. The labor investment of the crafter, the esoteric knowledge used to create the objects, and the identity of the possessor(s) all contributed to the legacy of jades as inalienable possessions. Jades were gifted, displayed, interred, and even destroyed in honor of the history, memory, prestige, and identity of the object and of the possessor, which were mutually constituted. Jades that were once thought to simply legitimate the elite prestige may have had nested social meanings, and the concept of inalienable possessions can help us to understand that complexity. [ABSTRACT FROM AUTHOR]

In 1902 R M Wood published the paper ''On a remarkable case of uneven distribution of light in a diffraction grating spectrum'' [1]. As was true of so much of his work, interest in his observations took flight, inspiring extensive research into associated new optical phenomena. What is now known as Wood''s anomaly has been described as the result of excitations of oscillations in the conducting electron plasma, or ''plasmons''. These quasiparticles have become increasingly attractive to researchers, perhaps less for the dazzling colours they impart to glitzy gemstones over their potential to facilitate medical imaging, as well as integrated optics [2] and the transfer of information and energy at dimensions below the diffraction limit. Excitation of surface plasmons provides a means of enhancing optical near fields, thus empowering a range of signal detecting applications. A range of innovative techniques have been implemented to probe surface plasmon resonances. The evolution of plasmon resonance energy and mean free path as particle dimensions increase from nanostructures to bulk matter has been monitored through ellipsometry, thus providing an insight into the plasmon polariton coupling [3]. Electron energy loss experiments have also proved a valuable tool for mapping surface plasmons with a spatial resolution an order of magnitude better than can be achieved with scanning near-field optical microscopes [4]. The exploitation of surface plasmons is primed to aid advances in medical imaging, diagnosis and therapy. Researchers in the US have developed a protein-enabled strategy to fabricate quantum dot nanoarrays where an increase in surface-plasmon-enhanced fluorescence of up to a factor of 15 has been achieved [5]. Understanding and dexterity in manipulating these enhancements has reached a high level of sophistication, and researchers in London have demonstrated the ability to increase the fluorescence enhancement by a factor of 4 and the decay rate by a factor of almost 30 by tuning the localised surface plasmon resonance of silver particle arrays to the emission wavelength of a locally situated fluorophore [6]. In the US and Belarus researchers have collaborated to investigate the potential of plasmonic nanobubbles, generated by laser activated nanoparticles, for combined diagnostics, therapy, and therapy guidance. Such nanobubbles can be optically tracked in the body, and their rapid expansion and collapse provides a localised mechanical impact on cells that can disrupt the cell membrane [7]. Surface plasmon polaritons at nanostructures allow highly local control of light, which has a range of uses in electronic devices. Photovoltaics researchers in the US and the Netherlands have demonstrated enhanced short circuit current densities compared to cells having flat or randomly textured back contacts using nanostructured plasmonic back contacts, which maximise the interaction with the light [8]. Progress in optoelectronics is another area where surface plasmon polaritons are playing an increasingly important role [9]. In this issue, researchers at the Institut des Sciences Mole culaire d''Orsay demonstrate that it is possible to excite propagating surface plasmon polaritons with a scanning tunnelling microscope, and detect them [2]. Their work also investigates the nature of the excited plasmons and how the intensities of the propagating surface plasmon polaritons and the localized plasmon emission can be enhanced by factors of 2 and 20 respectively by using a silver tip instead of a tungsten one. Wisdom may be worth more than silver and gold, but a little silver and gold can contribute a lot to unearthing new wisdom at the nanoscale. References [1] Wood R M 1902 Nanotechnology 18 296 [2] Wang T, Boer-Duchemin E, Zhang Y, Comtet G and Dujardin G 2011 Nanotechnology 22 175201 [3] Oates T W H and Mucklich A 2005 Nanotechnology 16 2606 [4] Bosman M, Keast V J, Watanabe M, Maaroof A I and Cortie M B 2007 Nanotechnology 18 165505 [5] Zin M T, Leong K, Wong N-Y, Ma H, Sarikaya M and Jen A K-Y 2009 Nanotechnology 20 015305 [6] Cade N I, Ritman-Meer T, Kwakwa K A and Richards D 2009 Nanotechnology 20 285201 [7] Lukianova-Hleb E Y, Hanna E Y, Hafner J H and Lapotko D O 2010 Nanotechnology 21 085102 [8] Ferry V E, Verschuuren M A, Li H B T, Verhagen E, Walters R J, Schropp R E I, Atwater H A, and Polman A 2010 Optics Express 18 A237-45 [9] Maier S A 2006 IEEE J. Sel. Top. Quantum Electron. 12 1671-7 [ABSTRACT FROM AUTHOR]

Several letters to the editor are presented in response to articles including "Mineral Oddities" by Robert Cook in the January/February 2009 issue and "Spessartine from Navegadora Mine, Minas Gerais, Brazil" by John White in the January/February 2009 issue, and one which calls for papers for the Gem and Mineral Show on February 13, 2010.

Abstract: Ba0.5Sr1.5Zn2Fe12O22 is a new promising multiferroic compound in which the existence of electric polarization is conditioned by the noncollinear arrangement of the iron spins. In principle, ferroelectricity might be present above the room temperature, but electrical conductivity prevents its observation at temperatures higher than ≈130K. Our recent calculations showed that the electronic structure and in particular the conductivity is strongly influenced by relative fractions of iron and zinc in the tetrahedral sublattice of the spinel block in corresponding Y hexaferrite structure. In this paper, we show that the same holds for the exchange interactions. Dependence of the exchange integrals on the distribution of iron and zinc in the tetrahedral sublattice of the spinel block and on the content of Sr in Ba2− x Sr x Zn2Fe12O22 system is calculated using the ab initio approach with an improved treatment of strongly correlated 3d electrons of iron ions. The interaction between the two magnetic blocks that is decisive for the phase diagram is analysed in details. [Copyright &y& Elsevier]

Investigation of scandium incorporation in garnets along the synthetic Ca3Fe23+Si3O12-Ca3Sc2Si3O12 (adr--CaSc) join, based on the same multi-technique approach used in the companion paper (Oberti et al. 2006a), shows that (1) Sc is incorporated exclusively at the Y octahedron; (2) the local coordination of Sc is slightly different in Sc-poor than in Sc-rich compositions (Sc-O = 2.06 Å in CaSc10 vs. 2.10 Å in CaSc30-90); (3) the local coordination of Ca is also slightly different in Sc-poor than in Sc-rich compositions [Ca1,2-O are 2.34(2) and 2.48(2) Å in CaSc10 and 2.36(2) and 2.50(2) Å in CaSc90, with Δ fixed at 0.14 Å in all the samples]; (4) the linear increase of the unit-cell edge along the join derives from multiple changes in the geometry of the different polyhedra and from the rotation of the tetrahedron around the 4̅ axis (α rotation), and cannot be modeled from extrapolation of the behavior observed along the Ca3Al2Si3O12-Ca3Fe23+Si3O12 (grs--adr) join. CaSc-rich garnets, where a large X dodecahedron coexists with a large Y octahedron and a Z tetrahedron occupied by Si, similar to pyrope-grossular garnets, have the highest a values observed to date in calcium silicate garnets. Slightly lower α values are observed in pyrope and almandine, but correspond to a different structural arrangement, where a small X dodecahedron coexists with a small Y octahedron. These results further confirm the efficiency of a combined short- and long-range approach for understanding the properties of garnet solid solutions. [ABSTRACT FROM AUTHOR]

The growth history reconstruction of tourmaline macro-crystals from pegmatite pockets in the aplite veins of Grotta d.Oggi (island of Elba, Italy) was carried out using a multi-disciplinary and multi-analytical approach [X-ray diffraction topography (XRDT) and electron microprobe analysis (EMPA)]. The work covered in this paper is closely related to the previous crystal-chemical characterization of the same macro-crystals (Bosi et al. 2005). The tourmalines examined here are bi-colored crystals exhibiting greenish-yellow to colorless zoning perpendicular to and parallel to the c axis: the transition from the inner yellow regions to the colorless ones occurs suddenly. XRDT and EMPA studies show relationships between color and chemical zoning and crystal growth evolution, thus identifying two main growth stages, which developed under different conditions. The first stage corresponds to greenish-yellow Mn-tourmaline grown as a result of a 2D-growth mechanism in a F-rich pegmatitic environment; the second one corresponds to colorless elbaitic tourmaline, which developed chiefly by a spiral growth mechanism in an OH-rich hydrothermal environment. The structural defects found in greenish-yellow Mn-tourmaline (growth bands, absence of dislocations, near-uniform chemical element concentrations) are the same as those observed in beryl crystals from pegmatite pockets of the island of Elba. Therefore these features are growth marks that characterize the pegmatitic crystallization stage and differentiate it from the hydrothermal stage, in which the dislocations normal to the growing faces occurred. Hence, the role of tourmaline as a petrogenetic indicator can be extended from chemical composition to crystal growth, reflecting both chemical environment and growth mechanism, and contributing to a better understanding of mineral genesis in pegmatitic crystallization. [ABSTRACT FROM AUTHOR]

The electronic properties of heavily doped (1020–1021 [B]/cm3) p+ diamond epilayers have been investigated in the article [1] featured as Editor's choice of the present issue. Free holes affect strongly the room-temperature optical response of such monocrystalline films in the range of phonon energies. This is illustrated by the IR reflectance and edge-view micro-Raman polarized scattering spectra shown in the cover figure. The corresponding author, Etienne Bustarret, heads the Semiconductors Group of the Laboratoire d'Etudes des Propriétés Electroniques des Solides of CNRS in Grenoble, focusing on the growth of diamond and on the structural and optical properties of epitaxially grown layers and devices based on silicon carbide, diamond or nitrides. The paper was presented as an invited lecture at the 8th International Workshop on Surface and Bulk Defects in CVD Diamond Films (SBDD VIII), held in Diepenbeek-Hasselt, Belgium, 26–28 February 2003. [ABSTRACT FROM AUTHOR]