Laser Induced Breakdown Spectroscopy can provide a useful contribution in mineralogical field in which the quantitative chemical analyses (including the evaluation of light elements) can play a key role in the studies on the origin of the emeralds. In particular, the chemical analyses permit to determine those trace elements, known as fingerprints, that can be useful to study their provenance. This technique, not requiring sample preparation results particularly suitable for gemstones, that obviously must be studied in non-destructive way. In this paper, the LIBS technique was applied to distinguish synthetic emeralds grown by Biron hydrothermal method from those grown by Chatham flux method. The analyses performed by collinear double-pulse LIBS give a signal enhancement useful for the quantitative chemical analyses while guaranteeing a minimal sample damage. In this way it was obtained a considerable improvement on the detection limit of the trace elements, whose determination is essential for determining the origin of emerald gemstone. The trace elements V, Cr, and Fe and their relative amounts allowed the correct attribution of the manufacturer. Two different methods for quantitative analyses were used for this study: the standard Calibration-Free LIBS (CF-LIBS) method and its recent evolution, the One Point Calibration LIBS (OPC-LIBS). This is the first approach to the evaluation of the emerald origin by means of the LIBS technique.

The application of the Laser Induced Breakdown Spectroscopy (LIBS) to gemmological materials is well known for the gemstone treatment detection but LIBS can also provide a useful contribution in mineralogical studies in which the chemical analyses is essential, playing a key role in the studies on the origin of minerals (Agrosì et al., 2014). The possibility to detect simultaneously all elements, including also light elements such as boron, lithium, and beryllium in a fast way and without sample preparation its clearly a great advantage of the LIBS. Moreover this technique is able to detect chromophorous elements even if they are in very low concentration. Nevertheless the main problems affecting LIBS are the difficulties to perform quantitative analyses and the partial destructivity of the method. Recently, with the development of the technique and in particular with the development of a new softwares there is also the possibilities to perform quantitative analyses with or without calibration. The last examples are the standard Calibration-Free LIBS and the One Point Calibration LIBS, CF-LIBS and OPC-LIBS respectively (Cavalcanti et al., 2013). The improvement of the instrumentation performance and the possibility to focalize the laser beam with an optical lens of a microscope allow to obtain an high resolution and a low destructivity of the sample. Moreover, the use of a double-pulse laser produce a signal enhancement useful for the quantitative chemical analyses guaranteeing a minimal sample damage. In this way we may obtain a considerable improvement on the detection limit of the trace elements, whose determination is essential to define the origin of gemstones. In the mineralogical studies the μ-LIBS appear very attractive because the possibility to select the smallest sampling areas ensures a better reconstruction of the chemical zoning and consequently allows to stimate the rock forming condition because the chemical zoning is sensitive to the changing of the physical and chemical parameters. Some cases of study have been performed on beryls and corundums with different objectives and the results will be discuss.

In recent years several studies were focused on the calculation of residual pressure around mineral inclusions in diamond in order to provide useful information on the depth of diamond origin. In these studies, the calculations were carried out using mainly vibrational spectroscopy data and were based on different assumptions including also the following important postulations: the diamond deforms elastically, no plastic or brittle deformation taking place during transportation to the surface, and the remnant pressure of the inclusion is the only cause of strain in the diamond that results in anomalous birefringence. [1] An helpful tool to verify the existence conditions of the aforementioned assumptions can be obtained by the analyses of structural defects using X-Ray Diffraction Topography (XRDT), a non-destructive imaging technique, sensitive to the strain associated with extended defects. This technique is particularly suitable for providing information about crystal growth and genetic environment of minerals by recording the spatial distribution of lattice defects and by the discrimination between growth and post-growth defects [2, 3, 4]. In this study a natural diamond from Finsch mine (South Africa) was investigated by XRDT in transmission geometry, using MoKα1 radiation with conventional source. The sample (F118) was a polished plate, about 1mm thick and cut perpendicular to [111]. The plate showed anomalous birefringence and a typical triangular shape with a rounded side in which re-entrant corners could be seen. X-ray topographs show that the sample is actually a mosaic crystal that developed through aggregation of individuals during growth: some slightly rotated relative to one another and others twinned. The twin law is by reticular merohedry and consists of the well-known 2-fold rotation around [111]. The larger inclusions are garnet crystals absorbed in the inner part of an individual showing triangular shape. No dislocations are nucleated from them. A number of inclusions were adsorbed at the interfaces between the twinned individuals and at the grain boundaries. Bundles of dislocations run from the smaller inclusions adsorbed in the outer region of the triangular individual. In the whole sample and chiefly in the regions showing a lower density of inclusions, packed lamination lines parallel to an octahedral face can be observed. These laminations represent a polysynthetic twinning commonly observed in diamonds when a plastic deformation occurs and thus can be considered post-growth defects. Finally, this study results useful to determine the strains associated to the inclusions and the presence of plastic deformation related to post-growth defects and thus can contribute to select the diamond samples and the inclusions suitable to provide information on the depth of diamond origin.

Two crystals of brown diamonds, coming from Argyle and Udachnaya, were studied, in a non-destructive way, by means of X-Ray Diffraction Topography (XRDT) with the aim to elucidate the relationships between the structural defects and the growth history. The sample from Argyle mine, labelled Br11, was a light-brown diamond with an irregular tetrahedral morphology and free of inclusions. Br11 shows a complex intergrowth phenomenon: the analyses of the diffraction contrasts and the optical observations reveal that the sample is really formed by two individuals twinned by the well-known spinel law. These individuals, in turn, are formed by different sub-individuals with different orientation, piled up along the [111] direction. An aggregation of numerous and thick lamellae parallel to the triangular morphology of the (111) face characterizes each sub-individual. Moreover, the XRDT images show partial dissolution followed by a final overgrowth. The sample from Udachnaya, labelled Ud02, was a light-brown diamond with an octahedral morphology that exhibits several large inclusions and fractures partially healed by dark epigenetic microinclusions. The analyses of the diffraction contrasts of the Ud02 sample show extended deformation fields, growth bands parallel to the octahedral faces and, in addition, a micro-lamination parallel to (1-1-1) that across the whole sample irrespectively of the different growth sectors. These laminations represent a polysynthetic twinning commonly observed in diamonds, which have undergone plastic deformation and are considered post-growth defects (Agrosì et al., 2013). No dislocations nucleated from the inclusions were observed. The analysis of the structural defects allows a reconstruction of a complex growth history of these samples characterized by a sequence of alternating episodes of growth, dissolution and plastic deformation. Lastly, the common feature of the micro-laminations was related to the origin of brown colour.

In recent years, several studies have focused on the growth conditions of the diamonds through the analysis of the mineral inclusions trapped in them. In these studies, it is crucial to distinguish between protogenetic, syngenetic and epigenetic inclusions. X-ray topography (XRDT) can be a helpful tool to verify, in a nondestructive way, the genetic nature of inclusions in diamond. With this aim, a diamond from the Udachnaya kimberlite, Siberia, was investigated. The diamond, previously studied by Nestola et al. (2011), has anomalous birefringence and the two largest olivines have typical “diamond-imposed” shapes. The study of the topographic images shows that the diamond exhibits significant deformation fields related to post growth plastic deformation. The absence of dislocations starting from the olivine inclusions, and the dark contrasts around them represent the main results obtained by XRDT, contributing to the elucidation of the relationships between the diamond and the olivines at the micron-meter scale. The dark halo surrounding the inclusions was likely caused by the effect of different thermo-elastic properties between the diamond and the inclusions. The absence of dislocations indicates that the diamond-imposed morphology did not produce the volume distortion commonly associated with the entrapment of the full-grown inclusions and, thus, only based on such evidence, a syngenetic origin could be proposed. In addition, stepped figures optically observed at the interface between diamond and one of the olivines suggest processes of selective partial dissolution that would contribute to a change in the final morphology of inclusions. These results show that a diamond morphology may be imposed to a full-grown (protogenetic) olivine during their encapsulation, suggesting that the bulk of the inclusion is protogenetic, whereas its more external regions, close to the diamond-inclusion interface, could be syngenetic.

In recent years, several studies have focused on the growth conditions of the diamonds through the analysis of the mineral inclusions trapped in them. In these studies, it is crucial to distinguish between protogenetic, syngenetic and epigenetic inclusions. X-ray topography (XRDT) can be a helpful tool to verify the genetic nature of inclusions in diamond. This technique characterizes, in a non-destructive way, the extended defects within a mineral and reconstructs the growth history of the sample (Agrosì et al., 2013). With this aim a diamond from the Udachnaya kimberlite, Siberia, was investigated. The diamond crystal was the one previously studied by Nestola et al. (2011) who performed in-situ crystal structure refinement of the olivine inclusions to obtain data about the formation pressure. Optical observations revealed an anomalous birefringence in the adjacent diamond and the inclusions had typical “diamond-imposed cubo- octahedral” shape for the largest olivines. The diffraction contrast study shows that the diamond exhibits significant deformation fields related to plastic post growth deformation. Section topographs revealed that no dislocations nucleated from the olivine inclusions. Generally, when a solid inclusion has been incorporated in full-grown state in another growing crystal, the associated volume distortion needs of a number of dislocations to ensure a better connection between the inclusion and the host phase. In some cases, complex twinning can be developed (Agrosì et al., 2013). In our case, the olivine assumes the morphology imposed from the diamond and, consequently, it does not produce volume distortion and the nucleation of dislocations is not necessary. This process generally occur during the simultaneously growth of the two minerals, confirming what was already stated by Bulanova (1995). However, the syngenetic nature of inclusions generally implies epitaxial relationship between diamond and inclusions that in our sample can be ruled out because the orientations of these olivines are random (Bruno et al., 2014). Therefore, the specific and significant results that characterize this sample will be discussed in detail.

n recent years, several studies have focused on the growth conditions of the diamonds through the analysis of the mineral inclusions trapped in them (Howell, 2012 and references therein). Nevertheless, to obtain rigorous information about chemical and physical conditions of diamond formation, it is crucial to determine if the crys- tallization of the inclusions occurred before (protogenetic nature), during (syngenetic nature) or after (epigenetic nature) the growth of diamond (Wiggers de Vries et al., 2011). X-ray topography (XRDT) can be a helpful tool to verify the genetic nature of inclusions in diamond. This technique characterizes the extended defects and reconstructs the growth history of the samples (Agrosì et al., 2013 and references therein) and, consequently contributes to elucidation of the relationship between the inclusions and the host-diamond. With this aim a diamond from the Udachnaya kimberlite, Siberia, was investigated. The diamond crystal was the one previously studied by Nestola et al. (2011) who performed in-situ crystal structure refinement of the inclusions to obtain data about the formation pressure. The inclusions were iso-oriented olivines that did not show evident cracks and subsequently could not be considered epigenetic. Optical observations revealed an anomalous birefringence in the adjacent diamond and the inclusions had typical “diamond-imposed cubo-octahedral” shape for the largest olivine. The diffraction contrast study shows that the diamond exhibits significant deformation fields related to plastic post growth deformation. The crystallographic direction of strains was established applying the extinction criterion. Section topographs were taken to minimize the overlapping of the strain field associate with the different defects and revealed that no dislocations nucleated from the olivine inclusions. Generally, when a solid inclusion has been incorporated in the growing crystal, the associated volume distortion can be minimized by means the nucleation of dislocations and/or twinning (Agrosì et al., 2013). In our case, the specific and significant features – the olivine inclusions showing a “diamond imposed cubo-octahedral shape” and no dislocation nucleation – that characterize this sample will be discussed in detail.