Near-Infrared Spectroscopy Study of Serpentine Minerals and Assignment of the OH Group

Three different kinds of serpentine mineral samples were investigated using Fourier transform near-infrared spectroscopy (FTNIR). The results show that there are obvious differences in the characteristic infrared spectra of the three serpentine group minerals (lizardite, chrysotile, and antigorite), which can easily be used to identify these serpentine minerals. The combination of weak and strong peaks in the spectrum of lizardite appears at 3650 and 3690 cm−1, while the intensities of the peaks at 4281 and 4301 cm−1 (at 7233 and 7241 cm−1, respectively) are similar. A combination of weak and strong peaks in chrysotile appears at 3648 and 3689 cm−1 and at 4279 and 4302 cm−1, and a single strong peak appears at 7233 cm−1. In antigorite, there are strong single peaks at 3674, 4301, and 7231 cm−1, and the remaining peaks are shoulder peaks or are not obvious. The structural OH mainly appears as characteristic peaks in four regions, 500–720, 3600–3750, 4000–4600, and 7000–7600 cm−1, corresponding to the OH bending vibration, the OH stretching vibration, the OH secondary combination vibration, and the OH overtone vibration, respectively. In the combined frequency vibration region, the characteristic peak near 4300 cm−1 is formed by the combination of the internal and external stretching vibrations and bending vibrations of the structural OH group. The overtone vibrations of the OH stretching vibration appear near 7200 cm−1, and the practical factor is about 1.965. The near-infrared spectra of serpentine minerals are closely related to their structural differences and isomorphous substitutions. Therefore, near-infrared spectroscopy can be used to identify serpentine species and provides a basis for studies on the genesis and metallogenic environment of these minerals.

A synthesis and meta-analysis of the Fe chemistry of serpentinites and serpentine minerals

The iron chemistry of serpentinites and serpentine group minerals is often invoked as a record of the setting and conditions of serpentinization because Fe behaviour is influenced by reaction conditions. Iron can be partitioned into a variety of secondary mineral phases and undergo variable extents of oxidation and/or reduction during serpentinization. This behaviour influences geophysical, geochemical and biological aspects of serpentinizing systems and, more broadly, earth systems. Iron chemistry of serpentinites and serpentines is frequently analysed and reported for single systems. Interpretations of the controls on, and the implications of, Fe behaviour drawn from a single system are often widely extrapolated. There is a wealth of serpentinite/serpentine chemical composition data available in the literature. Consequently, compilation of a database including potential predictors of Fe behaviour and measures of Fe chemistry enables systematic investigation of trends in Fe behaviour across a variety of systems and conditions. The database presented here contains approximately 2000 individual data points including both bulk rock and serpentine mineral geochemical data which are paired whenever possible. Measures of total Fe and Fe oxidation state, which are more limited, are compiled with characteristics of the systems from which they were sampled. Observations of trends in Fe chemistry in serpentinites and serpentines across the variety of geologic systems and parameters will aid in verifying and strengthening interpretations made on the basis of Fe chemistry. This article is part of a discussion meeting issue ‘Serpentinite in the Earth system’.

The Critical Role of Pulp Density on Flotation Separation of Nickel-Copper Sulfide from Fine Serpentine

A nickel-copper sulfide system usually coexists with serpentine in deposits. Low nickel-copper recovery and high content of serpentine in concentration adversely affects subsequent metallurgical processes. In this study, test data showed different rheological results at various densities. When the solid ratio of sulfide to serpentine was 1:1, lower pulp density (20 wt %) contributed to better rheological and flotation outcomes. Generally, the addition of SHMP (sodium hexametaphosphate) is beneficial to reduce the amount of serpentine mineral into the concentration as a depressant through changing the surface electrical behavior of serpentine. However, the different dosages of SHMP have little impact on pulp rheology at 40 wt % of slurry, but there is a huge difference on flow property at 20 wt % pulp. The results revealed that rheology, which is caused by pulp density, played a key role in flotation performance. The decline in density (from 40 wt % to 20 wt %) increased the nickel and copper recoveries from 70.7% to 79.5% and 82% to 85.4% respectively in the artificial mixture (1:1). The content of serpentine in concentration decreased by around 20% by using SHMP at the same time.

Utilization of Serpentine Resources in China

As a new type of non-metallic mineral resource, serpentine has attracted more and more attentions. Serpentine mineral resources are abundant in China, with more than 5 billion tons reserves proved. However, most of them have not been used adequately except for some special serpentine, such as serpentine jade and chrysotile. The overview for status quo of serpentine utilization consists of the distribution, chemical compositions, crystal structure of serpentine, mature but not economic applications and some development of high-value utilization research. It is expected to provide some references for deeper research and promoting its applications.

Provenance and Manufacture of Mixtec Style Objects Found on the Surrounding Structures of the Precinct of the Great Temple of Tenochtitlan

ABSTRACTSeventy six speckled greenstone items have been recovered on the surrounding structures of the Aztec precinct of the Great Temple of Tenochtitlan. Several researchers have identified the material as marble. Also, these objects have been labeled as Mixtec style due to the raw materials involved in their manufacture as well as their apparent similarity with other known Mixtec objects. The main objective of this essay is to determine the raw materials and the technology employed on its manufacture. Based on earlier composition analysis using Infrared spectroscopy (FTIR) and X-ray Fluorescence (XRF), it became clear that all items are made of the same calcite-serpentine mineral alloy, which probably comes from the Oaxaca region. It is interesting the homogeneity and standardization among these pieces by analyzing them with experimental archaeology and the characterization of their manufacturing traces. Comparing their raw material, morphology and techniques with those of Mixtec sites, the analysis revealed that they are not in fact related at all; however they do coincide with the manufacturing process of Tenochca (Aztec) style objects. This fact might point towards the actual origin of the raw materials, their obtainment and the technology behind the elaboration of luxury goods at Tenochtitlan.