Neoteric optical media for refractive index determination of gems and minerals

Refractive index determination of minerals and gems often requires their immersion in fluids with the same refractive index. However, these natural materials frequently have refractive indices above the ranges of common organic solvents. Most available high refractive index immersion materials are solid at room temperature, toxic, noxious, corrosive, carcinogenic, or any combination thereof. Since the physical properties of ionic liquids can be tuned by varying the cation and/or anion, we have developed immersion fluids for mineralogical studies which are relatively benign. We report here the syntheses of a range of ionic liquids ( many novel) based on the 1-alkyl-3-methylimidazolium cation, which all have refractive indices greater than 1.4, and can be used as immersion fluids for optical mineralogy studies. We further show that for a series of ionic liquids with the same anion, the refractive indices can be adjusted by systematic changes in the cation.

Varieties of resource nationalism in sub-Saharan Africa’s energy and minerals markets

This article examines resource nationalism in sub-Saharan Africa's energy and minerals markets. It does so by exploring economic and political developments in three cases: Nigeria as an example of a petro-state established by means of expropriation in the wake of decolonisation; South Africa, a mature mining industry shaped by its settler colonial history; and Mozambique, a new and therefore highly-dependent entrant into the league of significant natural gas producers. Extractive industries have played a controversial role in sub-Saharan Africa due in particular to the prevalence of the resource curse. Nevertheless, energy exports will continue to play an important role in fuelling economic growth and, potentially, also development as new deposits of natural gas and oil are discovered across the region. Resource nationalism has, moreover, increasingly constrained operations of the traditionally dominant Western energy companies, in particular as competition from state-owned energy companies in sub-Saharan Africa and from emerging powers such as China is increasing.

Accessory minerals and potentially toxic elements in Tanzanian vermiculites with respect to agricultural applications

The study assessed accessory minerals and metals in Tanzanian vermiculites with respect to their potential suitability for agricultural applications. Mineral and chemical analyses were involved. Pot experiments were also conducted to assess plant uptake of metals from soil with vermiculites. Fibrous sepiolite and amphiboles were minerals of health concern found in some samples. The sepiolite fibers had aspect ratios similar to those of asbestos minerals, which cause respiratory disorders and lung cancer when inhaled and thus pose a potential health risk to animals and humans. The amphibole fibers were thicker than 10 μm and are unlikely to be inhaled. Chromium (Cr) and nickel (Ni) concentrations in some samples were greater than the limits permitted in agricultural soils, but the elements are not highly plant available and do not inhibit the uptake of essential macronutrients. Heating vermiculites at 400-600° C enhanced extractability of Cr and Ni and should preferably be avoided. © Taylor & Francis Group, LLC.

Spectral Reflectance Characteristics of Kimberlite Indicator Minerals and Other Selected Mineral Grains

High chromium content in kimberlite indicator minerals such as pyrope garnet and diopside is often correlated with the presence of diamonds. In this study, kimberlite indicator minerals were examined using visible light reflectance spectroscopy to determine if chromium content can be correlated with spectral absorption features. The depth of absorption features in the visible spectral region were correlated with the molecular percentage of chromium and other first series transition metal elements obtained by electron microprobe data. In the visible part of the spectrum, chromium is evident by 3 absorption features in the pyrope reflectance spectrum; one isolated and narrow feature at the wavelength 689 nm was used to correlate with the chromium mol %. The isolation of this feature in the pyrope spectra is advantageous since it is not directly affected by other proximal absorption bands that could be caused by other transition metals. Analysis of the feature indicates that as grain volume increases the depth of the absorption feature will also increase. Clustering grain volumes into fractions yields better correlation between absorption depth and mol % chromium. Other types of garnet (almandine, grossular, spessartine) and kimberlite indicator minerals (olivine, diopside, chromite, ilmenite) were analyzed to determine if other absorption features could be used to predict the proportion of specific transition metal elements. Diopside in particular illustrates the same isolated chromium absorption feature as pyrope and may indicate mol percent but needs further study with larger sample sets.

Accounting for Human Rights Violations Risk: Conflict Minerals Mandatory Disclosures under the Dodd Frank Act

This paper examines the equity market response to firms’ disclosure of human rights violation risk with regard to conflict mineral usage as required by Section 1502 of the Dodd-Frank Act (the Act). This paper assesses the aggregate equity market response to regulatory events leading to the passage of the Act, the equity market reaction to voluntary early disclosures and mandatory disclosures of conflict mineral information in Form SD, as well as the determinants of the equity market response. Using a sample of 4,399 US registrants from January 1, 2008 to September 30, 2014, we document a significant negative stock market reaction to the passage of the Act and to conflict minerals disclosures on Form SD. The equity market reaction is more negative and limited to companies that source their minerals from conflict zones, companies with human rights violations, and companies with ambiguous disclosures. Taken together, the results of this study provide an economic justification for companies with poor conflict minerals practices to improve in order to avoid high costs that will arise if firms are forced to disclose human rights abuses. This paper also provides preliminary evidence that Form SD is successful in reducing the governance gap that exposes investors to unnecessary sanction, litigation and reputation risk from firms’ activities in conflict minerals usage.

Aproximació a l'estudi dels minerals a Cicle Inicial i Mitjà. 'Aproximación al estudio de los minerales en el Ciclo Inicial y Medio'.

Resumen basado en el de la publicación. Monográfico con el título: 'Geologia: idees i recursos educatius'

Minerals.

Los minerales son sustancias sólidas que forman las rocas y se originan en el interior profundo de la Tierra a elevadas temperaturas. Diferentes combinaciones de elementos forman diferentes minerales, los cuales pueden identificarse por su color, veta, forma, dureza, densidad, brillo. Los minerales han sido extraídos de los metales y piedras preciosas que los contienen, y se han utilizado para la pintura, la cerámica, las joyas e, incluso para dispositivos electrónicos. Al final del libro hay una pequeña bibliografía y direcciones de páginas web.