Crystal Chemistry Research of Minerals of Nigerite Group and Its Significance

There is a type of complex oxide mineral, composed of many elements such as Sn, Mg, Fe, Zn, Ti, Mn, Al, etc., in the areas of Anhua, Linwu and Shizhuyuan of Hunan Province. These minerals belong to nigerite, Mg-nigerite (pengzhizhongite), etc.. According to the principle of closest packing, the crystal chemical properties of nigerite (brown), pengzhizhongite (buff), Zn-nigerite (fawn), Fe-nigerite, Mn-nigerite (greenish-black) etc. have been analyzed. Their crystal structures may be characterized by O (the layers of cation octahedral coordinations), T_1 (the mixed layers of cation octahedral coordinations and cation tetrahedral coordinations in same directions), T_2 (the mixed layers of cation octahedral coordinations and cation tetrahedral coordination in different directions). The position of layer-O and layer-T is alternate permutation. The crystal structure of pengzhizhongite (6 H ) may be expressed by …OT_2OT_1OT_1…, taaffeite (8 H ), …OT_2OT_1OT_2OT_1…, and nigerite (24 R ), … OT_1OT_2 OT_2OT_1 …×3 etc.. In their structure, there are not only the crystal structure units of spinel … OT_2 OT_2 … but also the units of nolanite … OT_1 OT_1 …. The research of these minerals has important theoretic and practical significance in the fields of minerals, gemology, material science etc..

Ruby Occurrences in Turkey: Principle Characteristics

The G ksun Ophiolites in Do an ehir area (Malatya-Southern Turkey) contain corundum mineralizations with significant gem-quality (ruby). Modal mineralogical composition of ruby-bearing rocks consists of hornblende (65%-70 %), plagioclase (20%-25%), green garnet (4%-5 %), ruby (2%-3%), and opaque minerals (<1%). Although ruby shows varying colors in the groundmass, it is generally colorless and rarely very pale pink and has high relief. It has no cleavage but rotund fractures. It has highest interference colors and twinning in some poly-prismatic crystals under the microscope. Crystal sizes range from 2x10 mm up to 30x50 mm. The most remarkable properties are red to pink in color, low to medium transparency, medium to big crystal sizes, lamellar and deformation twinning, secondary liquid feathers, hollow tubes, mineral inclusions, asterism, high birefringence and refractive indices and specific gravity. Rubies show crimson red cathodoluminescence colors activated by Cr3+ in the crystal structure, which is confirmed by the Electron Probe Microanalyses (EPMA). Tectonic setting, geological environment, petrographical, mineralogical, geochemical and gemological characteristics of rubies suggest that the Do an ehir ruby mineralization can be classified into the amphibolite-hosted type of corundum deposits of Tanzania.

Natural amber, copal resin and colophony investigated by UV-VIS, infrared and Raman spectrum

Natural amber, copal resin and colophony are have investigated by UV-VIS, infrared and Raman spectrum. In order to distin- guish the natural amber, copal resin and colophony, we have successfully used the nondestructive examination （NDE） technology. The results show that UV-VIS could not distinguish these compositions. The infrared spectra can distinguish them, but the technology may destroy the specimen. The Raman spectra show three characteristic peaks of vibration near position 932 cmq and position 1179 cmq of copal resin, which confirm the existence of terpenes compounds in it. In the Raman spectra of colophony, the vibration characteristic peak at position 1589 cmq, caused by the conjugate double bond of internal unsaturated resin acid, is the basis of the characteristic difference between colophony and natural amber. The advantages of the distin- guished technology by Raman spectroscopy are convenient and nondestructive examination for natural amber, copal resin and colophony.