The real-time sensing of benzene, toluene, ethylbenzene, and xylene (BTEX) vapor has become urgent due to their widespread hazards. As a sensing platform that combines low energy consumption and high sensitivity, moisture-resistant detection of ppb-level BTEX vapor remains a challenge for quartz crystal microbalance (QCM) based gas sensors. In this work, we employed polyaniline nanofibers as the sensing material, significantly enhancing the QCM sensor’s detection capability for BTEX vapor down to the 50 ppb level. Besides, thanks to the hydrophobicity of polyaniline nanofibers, this sensor shows minimal response fluctuations to BTEX vapor in the relative humidity range of 50-90%. Furthermore, this sensor exhibits a short response time and excellent long-term stability, thereby presenting a broad prospect for future industrial applications in BTEX vapor detection. realtime real benzene toluene ethylbenzene (BTEX hazards sensitivity moistureresistant moisture resistant ppblevel level (QCM sensors work material s 5 Besides 5090%. 5090 90%. 90 50-90% Furthermore longterm long term stability 5090% 509 90% 9 50-90 50-9 50-

There is currently limited knowledge concerning South African coal deposits as hosts for rare earth elements (REE). This project aims to determine the concentration of REE, including yttrium and scandium (REY+Sc) in various coal seams and adjacent sediments in borehole cores from the Ermelo, Witbank, and Waterberg coalfields in South Africa. Coal petrography (maceral count and vitrinite reflectance), XRD, XRF, sequential chemical extraction procedure (SCEP) before ICP-MS, and mineral liberation analysis (MLA) were conducted on the coal and associated sediment samples. The coals were inertinite-rich, medium-rank bituminous coal, with moderate to high ash content. The two dominant minerals in all the coalfields are kaolinite and quartz, except for sample ZBS2M, where dolomite was dominant. The dominant major oxides are Al2O3, SiO2, Fe2O3, and CaO, which concur with the XRD results. The ICP-MS results following SCEP indicated that both coal and the associated sediments were light REY+Sc dominant. There was also an elevation of medium REY+Sc in the Witbank coal's associated sediment samples. Notably, the samples with the highest REY+Sc results were the sediment samples. The Waterberg samples had the lowest REY+Sc from both the coal (less than 2 μg/g to 7 μg/g) and associated sediments (2 μg/g to 15 μg/g). While the highest REY+Sc was yielded from the Witbank-associated sediments (500 μg/g to 2,500 μg/g). The carbonate fraction step proved to be the most successful leaching step, as most REY+Sc was recovered in that step for all coalfields. In addition to the carbonate fraction, the silicates and sulfide fraction in the Witbank samples, and the ion-exchangeable fraction for the Waterberg-associated sediments samples proved successful in leaching out the REY+Sc. MLA determined that monazite and xenotime in all the coal samples were the REY+Sc-bearing minerals.

Precast concrete products are load-tested to confirm compliance, but the workability of the concrete, being generally zero-slump concrete, is often not tested for quality control, as would be done with normal- or high-slump concrete. An industry practice in South Africa uses the percussive action of a rotary percussion drill to compact control cube samples. However, variability in specimen compaction leads to variations in the density and compressive strength results, making the procedure unreliable. This indicates a need for a simple, standardised quality control method for preparing zero-slump concrete cube samples with compaction equivalent to that achieved by precast machines. This technical note aims to (i) report on a practical and economical procedure (i.e. percussion-drill method) that has been formulated for quality control based on the concrete density achieved by precast machines, and (ii) apply this method to mix optimisation with the specific objective of partial replacement of the cement in a factory mix with a suitable fine filler to reduce cost and the carbon footprint of a precast facility. It was shown that the percussion-drill method was able to obtain reliable results (density, compressive strength) for quality control purposes and was successfully employed in the replacement of 17% to 32% of cement by volume with quartz flour in a factory mix. This resulted in a significant cost saving and a reduction in nett carbon emissions at the factory.

ABSTRACT The gold and silver deposits of the Vetas-California mining district are hosted in Paleozoic gneisses and Mesozoic granites of the Santander massif in the Eastern Cordillera of Colombia, far from the northern Andean volcanic arc. In the California area, there is ambiguity in defining the epithermal-type metallogenic model with high to intermediate sulfidation due to the presence of Late Triassic-Early Jurassic and Miocene magmatism. The best-known hydrothermal episodes comprise two early porphyritic-style phases: a) characterized by a propylitic alteration with molybdenite of the ∼10.1 Ma-old La Mascota breccia, related to granodiorite porphyries and smaller-volume rhyodacitic dykes; and b) attributed to a magmatic-hydrothermal system due to phyllic alteration associated with quartz-pyrite veins with hydrothermal sericite dated at ∼3.4 Ma. These two hydrothermal episodes were followed by four epithermal phases related to the development of multiphase hydrothermal breccias and quartz-alunite alteration, defined by bornite, covellite, and chalcopyrite, alongside wolframite, enargite, and sphalerite, with gold and silver mineralization between ∼2.6 and ∼ 1.6 Ma. To understand the relationship of the emplacement of the porphyries and the subsequent auro-argentiferous enrichments to the deformation front observed in the Pamplona buttress, to the east of the Santander Massif, a 4D structural model of the mineralization is formulated here. This model is based on the spatial analysis of the stresses responsible for the La Baja-Angostura dextral fault in terms of the regional kinematics of the Bucaramanga sinistral fault. It is considered that the SW sector of the deposit area corresponds to a well-defined, tabular, sub-vertical body of the La Mascota breccia. On the other hand, the NE sector in the La Baja-Angostura fault is expressed as a topographically elevated right horsetail splay, which controls the more disseminated distribution of the mineralization by means of veinlet swarms arranged in an ∼E-W direction. The disseminated mineralization of Vetas-California was probably favored by late thermal expansion-contraction events in the gneissic sockets, which allowed the accumulation and precipitation of boiling solutions rich in volatiles and elements of economic interest.

RESUMEN Los depósitos auroargentíferos del distrito minero Vetas-California están alojados en gneises paleozoicos y rocas ígneas mesozoicas del Macizo de Santander en la cordillera Oriental de Colombia, a cientos de kilómetros del volcanismo septentrional Norandino. En el área de California, existe ambigüedad en la definición del modelo metalogénico de tipo epitermal con sulfuración alta a intermedia debido a la presencia de magmatismo del Triásico tardío-Jurásico temprano y Mioceno. Los episodios hidrotermales mejor conocidos comprenden dos fases tempranas de estilo porfirítico: a) una caracterizada por una alteración propilítica con molibdenita de la Brecha La Mascota, de edad ∼10,1 Ma, relacionada con pórfidos de granodiorita y diques riodacíticos de menor volumen; b) otra atribuida a un sistema magmático-hidrotermal con alteración fílica asociada a filones y vetas de cuarzo-pirita con sericita hidrotermal de edad ∼3,4 Ma. A estos episodios le suceden cuatro fases de estilo epitermal relacionadas con el desarrollo de brechas hidrotermales multifásicas y con alteración de cuarzo-alunita, definidas por bornita, covelina y calcopirita, además de wolframita, enargita y esfalerita, con mineralización de oro y plata entre los ∼2,6 y ∼1,6 Ma. En la presente contribución se formula una hipótesis del modelo 4D del control estructural de las mineralizaciones para comprender la relación del emplazamiento de los pórfidos y los subsecuentes enriquecimientos auroargentíferos con respecto al frente de deformación reconocido en el Contrafuerte de Pamplona, al oriente del Macizo de Santander. Para ello, se analizan los esfuerzos responsables de la falla dextral La Baja-Angostura a partir de la cinemática regional de la falla sinistral de Bucaramanga. Se establece que el sector SO del área de mineralización corresponde a un cuerpo bien definido, tabular, subvertical, de la Brecha La Mascota. En el sector NE, en cambio, la Falla La Baja-Angostura se expresa como una cola de caballo (horsetail) derecha, topográficamente más elevada, la que controla la distribución diseminada de la mineralización mediante enjambres de vetillas subordinadas dispuestas en dirección principal ∼E-O. La mineralización diseminada de las Vetas-California fue favorecida probablemente por fenómenos tardíos de dilatación-contracción térmica de los encajantes gnéisicos, que permitieron la acumulación y precipitación de soluciones en ebullición ricas tanto en volátiles como en sustancias de interés económico.

In Southern Africa, historic mining and mineral processing of base metal deposits have almost exclusively focussed on the extraction of major metals, leading to the loss of remaining valuable raw materials into tailings dumps and waste rock piles. At the Namib Pb-Zn mine (Erongo Region, Namibia), historic base metal tailings deposits are present as unreclaimed exposed waste piles. The tailings comprise silt- (fraction A: d50 = 25 to 48 μm) to sand-sized (fraction B: d50 = 86 to 185 μm; fraction C: d5o = 210 to 230 μm) material and contain major concentrations of base metals (Pb av. 1.15 mass%, Zn av. 3.20 mass%), S (av. 9.95 mass%), as well as lower values of other metals (Cu av. 490 μg/g, Cd av. 133 μg/g, Ag av. 22 μg/g), and critical elements like Sb (av. 14.7 μg/g) and In (14.3 μg/g). Former mineral processing only targeted the extraction of galena and sphalerite. As a consequence, qualitative mineralogical composition of the tailings is similar to that of the primary ore. Ca-Fe-Mg(-Mn) carbonates, quartz, micas, chlorite, minor graphite, magnetite, and rare parisite relate to the former host rock and gangue matrix, whereas Fe-rich sphalerite, galena, magnetite, pyrite with minor pyrrhotite, rare arsenopyrite, marcasite, cassiterite, and accessory scheelite are original constituents of the primary ore. Reprocessing of such a material would be challenging, but a mixed Pb-Zn concentrate enriched in Cd and Ag might be obtained. In future, possible reprocessing of Namib tailings and associated disposal of wastes into an appropriately designed repository would not only generate valuable metal commodities, but such activities would also eliminate a major metal pollution source from the local environment.

Abstract In alluvial gold beneficiation, processes of heavy mineral concentration take place, many of which are of great economic interest. Among these, monazite is one of the most valuable, since it is an anhydrous orthophosphate of rare earth elements (ETRs), known for possessing extraordinary catalytic, electrical, magnetic, and optical properties. For this study, concentrate samples from the process tails of an alluvial gold operation, in El Bagre-Antioquia (Colombia) were used. The sample was subjected to gravimetric concentration, magnetic and electrostatic separation, in order to obtain monazite concentrate as pure as possible. To optimize the mineralogical characterization, the concentrate was separated into several granulometric fractions, from which grains from the coarsest fractions were selected using a binocular loupe, to be subsequently analyzed by FTIR and SEM, as support, for interpreting XRD results. Six main mineral phases were found: monazite, clinochlore, almandine, clinozoisite, zircon and ferroactinolite. Additionally, other minerals were identified in smaller quantities such as calcite, phlogopite, siderite, dolomite, quartz, ferrosilite and chromite, indicating that the concentration process was not efficient and could have negative effects on the extraction processes of ETRs, which could result in impure products. In this regard, improvements to the current monazite concentration process are proposed, based on the results of process mineralogy and the differences in their gravimetric, magnetic, and electrostatic susceptibilities.

Resumen En el beneficio del oro aluvial se dan procesos de concentración de minerales pesados, muchos de ellos de gran interés económico. Dentro de estos, la monacita es uno de los más preciados, ya que se trata de un ortofosfato anhidro de elementos de las tierras raras (ETRs), conocidos por poseer extraordinarias propiedades catalíticas, eléctricas, magnéticas y ópticas. Para este trabajo fueron utilizadas muestras de concentrado procedentes de las colas de proceso de una operación aluvial de oro en Cambiar por: El Bagre-Antioquia (Colombia). A la muestra se le practicaron procesos de concentración gravimétrica, separación magnética y electrostática, con el fin de obtener un concentrado de monacita lo más puro posible. Para optimizar la caracterización mineralógica, el concentrado fue separado en varias fracciones granulométricas, de las cuales fueron seleccionados los granos de las fracciones más gruesas mediante lupa binocular, para ser posteriormente analizados por FTIR y SEM, como soporte, para la interpretación de resultados de DRX. Se encontraron seis fases minerales principales: monacita, clinocloro, almandino, clinozoisita, zircón y ferroactinolita. También, se identificaron otros minerales en cantidades menores como la calcita, flogopita, siderita, dolomita, cuarzo, ferrosilita y cromita, lo que muestra que el proceso de concentración no fue eficiente y podría tener efectos negativos en los procesos de extracción de ETRs, lo cual podría resultar en productos impuros. En este sentido, se proponen mejoras al proceso de concentración de monacita actual, con base en los resultados de la mineralogía del proceso y en las diferencias de sus susceptibilidades gravimétricas, magnéticas y electrostáticas.

Abstract The potential reactivity against the alkali-silica reaction of gravels from a quarry located near Villalonga town, Patagones district (province of Buenos Aires) was evaluated. The petrographic analysis was carried out according to IRAM 1649 standard test method. Also the accelerated mortar bar test (IRAM 1674), and the conventional and accelerated concrete prism test method (IRAM 1700) were used, in accordance with the requirements for concrete coarse aggregates established in IRAM 1531 standard. Partially altered volcanic glass, varieties of cryptocrystalline silica and, minor microcrystalline quartz, were identified as potentially reactive components. The expansion measured in mortar bars and concrete prisms exceeded the maximum limit established in the standards, qualifying the aggregate as moderately reactive (R1) (IRAM 1531). Finally, a pessimum effect was observed when replacing 40% of the gravel with a non-reactive sand, registering 0.36% expansion in the accelerated mortar bar test after 16 days of testing.

Resumen Se evaluó la potencial reactividad frente a la reacción álcali-sílice de cantos rodados provenientes de una cantera ubicada en proximidades a la localidad de Villalonga, partido de Patagones (provincia de Buenos Aires). Se realizó el análisis petrográfico según la norma IRAM 1649, el ensayo acelerado de la barra de mortero (IRAM 1674) y el método del prisma de hormigón convencional y acelerado (IRAM 1700) de acuerdo con los requisitos establecidos para los agregados gruesos para hormigón (IRAM 1531). Se identificaron vidrio volcánico parcialmente alterado, variedades de sílice criptocristalina y, en menor proporción, cuarzo microcristalino, como componentes potencialmente reactivos. La expansión medida en las barras de mortero y en los prismas de hormigón superó el límite máximo establecido por norma, calificando al agregado como moderadamente reactivo (R1) (IRAM 1531). Por último, se observó un efecto pessimum al reemplazar 40% del canto rodado por una arena no reactiva, registrándose 0,36% de expansión en el ensayo acelerado de la barra de mortero a 16 días de ensayo.

Abstract The objective of this study was to determine the mineralogical composition of equine enteroliths from the Aburrá Valley in Antioquia, Colombia. Samples of eight enteroliths from eight horses were subjected to semi-quantitative X-ray diffraction (XRD) and transmission and scanning electron microscopy (TEM/SEM) analysis. The TEM/SEM of the analyzed enteroliths reported the presence of carbon, oxygen, phosphorus, magnesium, calcium, silicon, potassium, bromine, iron, sulfur, and aluminum. The XRD identified struvite, newberyte, kyanite, low quartz, actinolite, nitratine, cordierite, and vivianite. Both techniques used in the analysis of the enteroliths were correlated by matching the mineral compounds with the detected chemical elements. The main mineral components of the enteroliths were magnesium phosphates, struvite and newberyte being the most common.

Resumen El objetivo de este estudio fue determinar la composición mineralógica de enterolitos de equinos del Valle de Aburrá, Antioquia, Colombia. Muestras de ocho enterolitos de ocho caballos, fueron sometidas a análisis por Difracción de Rayos X Semicuantitativo (DRX) y microscopía electrónica de transmisión y barrido (METB). La METB de los enterolitos analizados reportó carbono, oxígeno, fósforo, magnesio, calcio, silicio, potasio, bromo, hierro, azufre y aluminio. A través de DRX se identificó estruvita, newberyta, kyanita, quartz low, actinolita, nitratina, cordierita, vivianita. Ambas técnicas empleadas en el análisis de los enterolitos se correlacionaron al coincidir los compuestos minerales, con los elementos químicos determinados. Los principales componentes minerales de los enterolitos fueron fosfatos de magnesio, siendo la estruvita y la newberyta los más comunes.

The hydrogeological conditions in the Chambishi mine area in Zambia. were investigated. Chambishi is a very wet mine and groundwater discharge costs are high. The research goal was to identify methods to reduce the discharge costs without greatly affecting the mining process. Hydrogeological data was obtained from measurements in drill-holes and from drill cores. The differences in structural deformation in different areas determine whether a layer of rock is an aquifer. In the mine region, the Lower Roan Group ore shale and quartz-sandstone unconformably lie on the basal schist and granite aquifuge. The Upper Roan Group dolomite is continuously distributed over a large area around the orebody. This dolomite is the main target of groundwater control efforts, and its water yield is also influenced by the deformation intensity. Based on the observations, backfilling was gradually adopted to appropriately safeguard the integrity of the aquifuge above the orebody. The overlapping relationship between the aquifer and aquifuge has been utilized to increase mine drainage efficiency. This measure has not only greatly reduced the costs of mine drainage, but also improced protection of the groundwater environment. The old drill-holes that were not sealed after exploration drilling were grouted. Further, possible water-conducting fracture zones were investigated. Cover drilling towards the suspected zone was conducted to prevent the high-pressure groundwater from shallower aquifers from entering stopes in deep areas of the mine.

Different concentration techniques were evaluated for preconcentration of a mineral ore at a coarser size to avoid energy and resource wastage. Specifically, the aim was to reduce milling costs and energy required in the beneficiation of tin. In this study, cassiterite (0.17% Sn) was the mineral of interest in a pegmatite ore body associated with quartz (SiO2 > 60%) and alumina (Al2O3 > 20%). Three concentration techniques, namely dense media, shaking table, and flotation, coupled with characterization analysis, were used to assess the concentration response. The results confirmed that particle size and mineral liberation impact the separation process. High recovery and grade were obtained with gravity concentration methods (dense media and shaking table) for coarser (+300 to +212 μm) and intermediate (+150 to +53 μm) particle sizes. Lower recovery and grade were identified for much finer sizes (-53 to -38 μm). Flotation produced a high-grade product at a relatively low recovery and appeared to be only applicable to finer grains. Separation efficiency based on Schulz's equation measured a segregation performance of 74.8% for dense medium separation and 60.7% for the shaking table for the coarse and intermediate particle sizes. Flotation only achieved a separation of 30%-40%. The results suggest that use of dense media separation as a rough preconcentration method prior to further grinding, and the utilization of a more advanced concentration technique for mineral recovery and upgrade, constitute a successful approach to improve process economics.

Tribo-electrostatic separation is a promising method for effectively utiliing low-grade magnesite resources by removing quartz and improving the grade of magnesite. To determine the charge-to-mass ratios of pure magnesite and quartz, a triboelectric measurement system was employed, and a laboratory tribo-electrostatic separation system was used to separate low-grade magnesite. The results showed that the maximum difference in charge-to-mass ratio between pure magnesite and quartz particles was observed after friction with polyvinyl chloride. The grade and recovery of magnesite increased with temperature and initially increased with increasing voltage, feed rate, and air flowrate before gradually decreasing. The optimal conditions resulted in a concentrate with 46.91% MgO content and 77.36% recovery, while the quartz content decreased from 7.02% to 1.95%. These experimental results demonstrate the effectiveness and potential of tribo-electrostatic separation in removing quartz and upgrading magnesite.

Abstract: Soil is the basic material for the manufacture of compressed earth bricks, which is worked without any type of stabilization to obtain the minimum physical and mechanical properties required according to Peruvian standard E.070. The objective of this research is to evaluate the physical and mechanical characteristics of compressed earth bricks stabilized with different dosages of 5, 8, 12, 12, 15 and 18% of cement in dry weight of soil. The tests performed were: absorption, compressive strength, flexural strength per unit of masonry, compressive strength in piles, diagonal compressive strength of walls and the X-ray diffraction test. The results obtained show that with 18% of cement the optimum resistance is obtained, in terms of compressive strength increased by 53.95%, flexural strength by 43%, pile compressive strength by 36.6%, and wall diagonal compressive strength by 41.24%, respectively. The X-ray diffraction test applied to the optimum stabilized compressed earth brick sample shows that its composition is dominated by certain components such as 32.4% calcium silicate, 23.8% aluminum silicate, 17.4% hydrated calcium, 14.2% illite, 6.86% calcium oxide, 3.34% quartz, 1.2% kaolinite and 0.8% goethite. It is concluded that cement-stabilized compressed earth bricks (LTCEC) are a sustainable construction alternative that improves the mechanical properties of earth bricks.

Resumen: El suelo es el material básico para la fabricación de ladrillos de tierra comprimida, el cual se trabaja sin ningún tipo de estabilización para obtener las propiedades físicas y mecánicas mínimas requeridas según la norma peruana E.070. El objetivo de esta investigación es evaluar las características físicas y mecánicas de ladrillos de tierra comprimida estabilizados con diferentes dosificaciones de 5, 8, 12, 15 y 18% de cemento en peso seco de suelo. Los ensayos realizados fueron: absorción, resistencia a la compresión, resistencia a la flexión por unidad de mampostería, resistencia a la compresión en pilas, resistencia a la compresión diagonal de muros y el ensayo de difracción de rayos X. Los resultados obtenidos muestran que con 18% de cemento se obtienen la resistencia óptima, en términos de resistencia a la compresión aumenta en un 53.95%, resistencia a la flexión en un 43%, resistencia a la compresión en pilas en un 36.6%, y resistencia a la compresión diagonal de muros en un 41.24%, respectivamente. La prueba de difracción de rayos X aplicada a la muestra óptima de ladrillo de tierra comprimida estabilizada muestra que en su composición predominan ciertos componentes como 32.4% de silicato de calcio, 23.8% de silicato de aluminio, 17.4% de calcio hidratado, 14.2% de illita, 6.86% de óxido de calcio, 3.34% de cuarzo, 1.2% de caolinita y 0.8% de goethita. Se concluye que los ladrillos de tierra comprimida estabilizados con cemento (LTCEC) son una alternativa de construcción sostenible que mejora las propiedades mecánicas de los ladrillos de tierra.

Abstract Oyola 51 is an archaeological site identified in the town of Oyola, El Alto department, Catamarca province. It was interpreted as a domestic space. Even so, it does not fully conform to the homes already studied in the area. Therefore, this work aspires to add information regarding the particular characteristics of this occupation and the practices that occured in it, which allow us to specify if it is indeed a domestic unit. This was carried out through the study of the knapped lithic technology recovered at the site. The techno-morphological and morpho-functional analysis of the lithic assemblage was carried out, evaluating specific variables and taking into account the different stages of the production sequence. The analysis of the lithic technology of a site of these characteristics allowed us to identify some practices carried out at the site and evaluate the differences observed with respect to other similar sites in the area. Likewise, the information obtained allowed us to add to the general knowledge of occupations at El Alto-Ancasti Mountain range, and the way in which the people who inhabited it related to their environment.

Resumen Oyola 51 es un sitio arqueológico ubicado en la localidad de Oyola, departamento El Alto, provincia de Catamarca. El mismo fue interpretado como un espacio doméstico. Aun así, no se amolda en su totalidad a las viviendas ya estudiadas en el área. Por esta razón este trabajo aspira a sumar información respecto a las características particulares de esta ocupación y de las prácticas acontecidas en la misma, que nos permita especificar si se trata de una unidad doméstica efectivamente. Esto se llevó a cabo a través del estudio de la tecnología lítica tallada recuperada en el sitio. Se realizó el análisis tecno morfológico y morfológico funcional del conjunto lítico, evaluando variables específicas y teniendo en cuenta las diferentes etapas de la secuencia de producción. El análisis de la tecnología lítica de un sitio de estas características permitió identificar algunas prácticas realizadas en el lugar y evaluar las diferencias observadas con respecto a otros sitios de vivienda del área. Asimismo, la información obtenida permitió sumar al conocimiento general de las ocupaciones en la Sierra de El Alto-Ancasti, y de la manera en que las personas que la habitaron se relacionaron con su entorno.

Abstract This article presents the results obtained from the techno-morphological and technological analysis of the lithic assemblage from surface collections in different sectors of the Laguna La Huinca site, located in the middle basin of the Tapalqué creek (Buenos Aires province). The main objective is to identify, from the reconstruction of the operational chains for each rock, the technological practices and trajectories of production used by hunter-gatherer groups that inhabited this sector of the basin, far from the sources of procurement. In general terms, a predominance of orthoquartzite was identified, followed by chert and, to a lesser extent, silicified dolomite, sandstone, diabase and quartz. Although this same trend in the representation of rocks is recorded at the Empalme Querandíes 1 and Laguna de Frías sites, this situation is not consistent with the rest of the sites for the upper and middle basin of the Tapalqué creek. Differences in the treatment of the rocks were identified, which is reflected in the diverse technological practices and modes of production of lithic artefacts. The scarce presence of cortex on flakes suggests that the initial stages of debarking were carried out off-site. The operational chains in orthoquartzite and chert are represented by stages ranging from lithic production, linked to the production of blanks, to the maintenance of the stone tools.

Resumen En este artículo se presentan los resultados obtenidos del análisis tecno-morfológico y tecnológico efectuado sobre el conjunto lítico proveniente de recolecciones superficiales en distintos sectores del sitio Laguna La Huinca, ubicado en la cuenca media del arroyo Tapalqué (provincia de Buenos Aires). El objetivo principal es identificar, a partir de la reconstrucción de las cadenas operativas para cada roca, las prácticas tecnológicas y las trayectorias de producción utilizadas por los grupos cazadores-recolectores que habitaron este sector de la cuenca, alejado de las fuentes de abastecimiento. En líneas generales, se identificó un predominio de la ortocuarcita, seguida por la ftanita y en proporciones ínfimas dolomía silicificada, arenisca, diabasa y cuarzo. Si bien se registra esta misma tendencia en la representación de las rocas en los sitios Empalme Querandíes 1 y Laguna de Frías, esta situación no se condice con el resto de los sitios para la cuenca superior y media del arroyo Tapalqué. Se identificaron diferencias en el tratamiento de las rocas, lo cual se ve reflejado en las diversas prácticas tecnológicas y en los modos de producción de los artefactos líticos. La escasa presencia de desechos de talla con corteza permite pensar que las etapas iniciales de descortezamiento se realizaron fuera del sitio. Las cadenas operativas en ortocuarcita y ftanita están representadas por las etapas que van desde la producción lítica, vinculada con la obtención de formas-base, hasta el mantenimiento de los artefactos formatizados.

Abstract In the county of Pedra Lavrada - PB, various mineral occurrences of pegmatite are observed with prominence at Alto Dois Irmãos - PB, where quartz, feldspar and mica are mined. The understanding of mineral constituents is fundamental to define their industrial employment and to implement improvements in the beneficiation process. The proposal of this research is the detailed characterization and proof of that part of the ore (quartz) considered waste, presenting low poisoning (Fe2O3) and high silica (SiO2) content, to enable its industrial use. Besides that, to minimize the environmental impact through the reuse of this waste, and to determine the correct utilization of the milling equipment. For the pegmatite characterization, done were density determination tests, mineralogical identification by X-ray diffraction (XRD), chemical analysis by fluorescents X-rays and morphological analysis by scanning electron microscopy (SEM/EDS). Then tests were done for the Work Index (WI) calculous and consequently the empirical determination of the dimensions (LxD) of the pebble mill. The sterile presented a medium density of 2.66g/cm³, majority chemical composition of silicon and oxygen and quartz as the main mineralogical stage, indicating that this material has high purity. The. The Work Index (WI) was 15.9 kwh/t showing that this material can be considered resistant to breaking in the grinding process. The necessary energy to the milling was defined in 11.52 kwh/st, that corresponds to 57.28 HP. This power allowed the mill selection with diammeter and length of 1.83m, that provides the production maximization and the energy saving. PB mined process (quartz waste Fe2O3 FeO Fe O (Fe2O3 SiO2 SiO (SiO2 content use equipment Xray X ray XRD, XRD , (XRD) Xrays rays SEM/EDS. SEMEDS SEM/EDS . SEM EDS (SEM/EDS) WI (WI LxD (LxD 266gcm³ gcm 2 66g cm³ g cm 2.66g/cm³ stage purity 159 15 9 15. kwht kwh t 1152 11 52 11.5 kwhst st kwh/st 5728 57 28 57.2 HP 183m m 1 83m 1.83m saving Fe2O (Fe2O (SiO (XRD (SEM/EDS 266gcm 2.66g/cm 115 5 11. 572 57.