Editorial for Special Issue 'Industrial Minerals'

Industrial minerals play an important role in keeping our society running, as they are used in a wide range of industrial and domestic applications. Harben and Bates [1] define the industrial minerals as all those materials that man takes out of the Earth’s crust, except for fuels, metallic ores, water, and gemstones. A commonly used synonym for industrial minerals is non-metallic minerals, and a more precise one is industrial minerals and rocks. Industrial minerals include minerals and rocks that, depending on their physical and chemical properties, are used, directly or with treatment, in the manufacturing of products, such as ceramics, glass, cement, biomaterials, and geopolymers, and even in the recycling of wastes. This definition also includes construction materials and waste products of several bulk industrial processes [2]. Compared with ore minerals, industrial minerals are cheap, as they are generally abundant, widely distributed on the Earth’s surface, and are often simple to process

Viability of bauxite deposits from Catalonia (Spain) for ceramic applications

This study provides a characterization of materials from wastes and outcrops of twoinactive bauxite mines located close to Sant Joan de Mediona and Peramola, Spain. Mineralogy wasdetermined via powder X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR).Thermal properties were measured via differential thermal analysis–thermogravimetry (DTA-TG) andgresification tests. The crystalline phases are medium-high crystalline kaolinite and variable amountsof illite, quartz, calcite, boehmite, hematite and rutile/anatase. DTA show two endothermic peaksproduced by the dehydroxylation of minerals: the first peak, at 530–538 C, belongs to boehmite; thesecond peak, at 535–568 C, corresponds to kaolinite. An exothermic peak at 950–978 C is associatedwith mullite crystallization. The optimal sintering temperatures obtained from the gresification curves(firing shrinkage and water absorption) were 970 C for carbonate-poor, illite-rich clays; 1100 C forillite- and carbonate-poor samples; and near 1190 C for carbonate-rich materials. The carbonate-poorsamples fired at 1300 C contain sillimanite and mullite, and the carbonate-rich materials are richin gehlenite, anorthite, and hedenbergite. The mineralogy of these materials is sufficient to obtainceramic materials with suitable properties, but not their low plasticity. They could be used in theformulation of bricks or as part of mixtures to produce refractory ceramics.</p

Are patinas of the Mediterranean monuments really related to the rock substrate?

Patinas of different mineralogies and colours occur on most monuments of the Mediterranean area. The origin(s) of the latter have often been related to previous painting and/or protective treatment(s). Microbial and biogeochemical pathways of formation, however, have as well been proposed and discussed. Paintings and photographs make it clear that coatings of changing colours have covered famous monuments in the past 200 years. Also the presence of microbiota has been recorded already 150 years ago. The work recorded here was done on several buildings in the Mediterranean area. A wide variety of localities and rock substrates and the patinas on them have been studied. Among the rocks were marbles, limestones calcarenites, granites and sandstones. In all cases studied patinas, their thickness and colour as well as their mineralogical composition were related to the exposure type. The patinas usually are multi-layered, the individual layers characterized by different crystal size, texture, mineralogy, and colour. Orange to grey layers are characterized by calcium carbonates and oxalates with some phosphates admixed, while the dark grey to black layers are rather characterized by gypsum with some trapped air-borne particles in cases. The petrology and mineralogy of the patinas is practically identical in all cases. Many of the patinas are inhabited by a variated microflora causing pitting and exfoliation in cases of the patina. Sometimes the pitting is only seen in the patina, and it reaches also the bedrock. A relationship between patina formation, preservation, destruction and climatic changes over the past 200 years is derived from these findings

Phosphorus solubility in basaltic glass: limitations for phosphorus immobilization in glass and glass-ceramics

The composition of sewage sludge from urban wastewater treatment plants is simulated using P-doped basalts. Electron microscopy analyses show that the solubility of P in the basaltic melt is limited by the formation of a liquid-liquid immiscibility in the form of an aluminosilicate phase and a Ca-Mg-Fe-rich phosphate phase. The rheological behavior of these compositions is influenced by both phase separation and nanocrystallization. Upon a thermal treatment, the glasses will crystallize into a mixture of inosilicates and spinel-like phases at low P contents and into Ca-Mg-Fe phosphate at high P contents. Hardness measurements yield values between 5.41 and 7.66 GPa, inside the range of commercial glasses and glass-ceramics. Leaching affects mainly unstable Mg2+-PO43- complexes

Mineralogical and thermal characterization of kaolinitic clays from Terra Alta (Catalonia, Spain)

This research characterizes the kaolinitic clays from Cretaceous-Paleocene lateritic depòsits of Terra Alta (south Catalonia) to evaluate their possible applications. The outcrops and quarries belong to the Horta de Sant Joan and Pinell de Brai areas. The chemical composition, mineralogy, rheological behavior, particle size distribution and plasticity are determined. The Fe and Ti4+ contents prevent them from being directly used as raw material for white ceramics. The mineralogy consists of kaolinite with quartz, illite, hematite, and minor K-feldspar and calcite. Most of the area comprises medium plastic clays that are classified as fired clays and can be used as ceramic and construction materials. In Horta de Sant Joan, a kaolinitic-rich level, up to 75 wt % of kaolinite, is highly crystalline with low plasticity and can be classified as flint clay, useful as a refractory clay. The evaluated kaolinitic clays can also be used to obtain a triaxial ceramic when they are mixed with feldspar to act as a fluxing agent and chamotte

Caracterización de los lignitos Garumnienses del Pirineo Central catalán

La Formación Tremp en los sectores de Berga, Tremp y Ager (Pirineo) presenta materia orgánica de tipo húmico, procedente de plantas terrestres y con una amplia variabilidad de resinita. Asociada a ella rellenando cavidades celulares, reemplazando o alternando en bandas se encuentra la fracción mineral, siendo mayoritariamente carbonática. El dominio de una fracción u otra está directamente relacionada con el momento de sedimentación y el ambiente deposicional

MINROCIND una eina d'aprenentatge presencial e interactiva dels jaciments de roques i minerals industrials a Catalunya. Eina d'aprenentatge presencial i/o interactiu en el àmbit dels ensenyaments de la mineralogia i petrologia aplicada

Es tracta d'un material i eina didàctica a la vegada. Té doncs una doble vesant: a) una part física constituïda per una mostra de roca polida i una làmina prima de la mateixa roca, per a ser utilitzada a l'hora de pràctiques a classe; i b) una part virtual formada per una base de dades interactiva on els estudiants trobaran fitxes amb les característiques bàsiques de la roca, i la descripció de les pedreres més importants on es troben i la seva importància com a recurs econòmic, com a roca ornamental i/o industrial

La vitrificación: un ejemplo de sostenibilidad ambiental

The accumulation of urban sewage sludge is an environmental problem to which solutions must be sought. One of the ideas proposed in this paper is to turn it into glass. Thus, from a 'useless' product we obtain a new, more valuable material. This solution addresses two environmental aspects and a conceptual one, because in order to understand the process it will be necessary to introduce new concepts related to crystalline and amorphous material, and this allows us to make a comparison with glass formation in natur

Estudio Arqueométrico de Cerámicas Procedentes de Gaoua: Burkina Faso

El objeto de este estudio es la caracterización arqueométrica de dos fragmentos cerámicos hallados alrededor de Gaoua, ciudad capital de la provincia de Poni (Burkina Faso). Aproximadamente en el medio del triangulo formado por los pueblos de Dimolo, Dipeò y Niantana, donde se encontraron restos de un poblado Lobi. Geológicamente, la región es de edad precámbrica, constituida por migmatitas y granitos con materiales volcanosedimentarios, meta-vulcanitas neutras y acidas, así como metasedimentos arcillosos (Hottin y Oueadraogo, 1976