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The Gavà phosphate deposit, mined during the Neolithic, was produced by weathering processes affecting primary apatite beds. It exhibits a neat vertical zoning, related to chemical gradients during weathering. Strengite, yellowish Al-rich strengite and ferroan variscite are found at the top, palegreen variscite at the intermediate levels, and green variscite in depth. Fe values are very low in the greenish samples, as well as Cr and V. Raman spectrums of the Gavà variscite show differences with samples from other occurrences worldwide. Moreover, some spectral differences can also be observed in the Raman spectra of variscite coming from different depths in the deposit. Raman spectroscopy can be an efficient tool to discriminate not only samples from different geographical localities, but also from its original position in a given deposit. Key-words: variscite, Raman, microprobe, veins, supergene. The Gavà phosphate deposit, mined during the Neolithic, was produced by weathering processes affecting primary apatite beds. It exhibits a neat vertical zoning, related to chemical gradients during weathering. Strengite, yellowish Al-rich strengite and ferroan variscite are found at the top, palegreen variscite at the intermediate levels, and green variscite in depth. Fe values are very low in the greenish samples, as well as Cr and V. Raman spectrums of the Gavà variscite show differences with samples from other occurrences worldwide. Moreover, some spectral differences can also be observed in the Raman spectra of variscite coming from different depths in the deposit. Raman spectroscopy can be an efficient tool to discriminate not only samples from different geographical localities, but also from its original position in a given deposit. Key-words: variscite, Raman, microprobe, veins, supergene. The Gavà phosphate deposit, mined during the Neolithic, was produced by weathering processes affecting primary apatite beds. It exhibits a neat vertical zoning, related to chemical gradients during weathering. Strengite, yellowish Al-rich strengite and ferroan variscite are found at the top, palegreen variscite at the intermediate levels, and green variscite in depth. Fe values are very low in the greenish samples, as well as Cr and V. Raman spectrums of the Gavà variscite show differences with samples from other occurrences worldwide. Moreover, some spectral differences can also be observed in the Raman spectra of variscite coming from different depths in the deposit. Raman spectroscopy can be an efficient tool to discriminate not only samples from different geographical localities, but also from its original position in a given deposit. Key-words: variscite, Raman, microprobe, veins, supergene.

Mining for iron resources in the Gavà area of Catalonia occurred intermittently during the Iberian and Roman epochs, the Middle Ages, and continuing until the industrial era, as evidenced by historical and archaeological documents. Iron mining in this area could have occurred even earlier, during the Neolithic period. Iron ores were formed in two stages: (1) a regional hydrothermal alteration associated with Hercynian thrusts that produced the ankeritization of limestones within the Paleozoic series, and (2) the karstic replacement of these iron-rich carbonates during the Pliocene and Quaternary by means of supergenic fluids that produced ochres with goethite and hematite. The style of mineralization largely depends on the characteristics of the replaced protolith, and three styles of mineralization can be defined: (1)The supergenic replacement of ankeritized massive Pridolian limestones only produced local replacements that were restricted to structural or stratigraphic discontinuities, therefore, the mineralization has reduced dimensions and occurs as irregular veinlets or pipes; (2) The replacement of interbedded ankeritized limestones and pyrite-bearing shales (Lockovian) produced massive ores in pod-shaped bodies rich in silica impurities derived from the altered shales; and (3) The replacement of carbonates overthrust by pyrite- and phosphate-rich shales favored the formation of massive stratabound deposits, which are the largest and highest grade deposits in the study area, and may be locally enriched in minerals of the alunite supergroup and Ca- and Fe-rich phosphates. Outcrops of all of these styles of mineralization were mined by the Iberian cultures, during the roman period and in the Middle Ages, taking advantage of the relatively high metallurgical quality of the ores.Therefore, the exploitation during these epochs was artisanal by means of trenches or small pits. In contrast, during the industrial era only the massive stratabound deposits were exploited in open pits and underground galleries.

The Gavà phosphate deposit, mined during the Neolithic, was produced by weathering processes affecting primary apatite beds. It exhibits a neat vertical zoning, related to chemical gradients during weathering. Strengite, yellowish Al-rich strengite and ferroan variscite are found at the top, palegreen variscite at the intermediate levels, and green variscite in depth. Fe values are very low in the greenish samples, as well as Cr and V. Raman spectrums of the Gavà variscite show differences with samples from other occurrences worldwide. Moreover, some spectral differences can also be observed in the Raman spectra of variscite coming from different depths in the deposit. Raman spectroscopy can be an efficient tool to discriminate not only samples from different geographical localities, but also from its original position in a given deposit. Key-words: variscite, Raman, microprobe, veins, supergene. Le gîte de phosphates de Gavà, exploité au Néolithique, s’est formé par des processus de météorisation qui auraient affecté des strates primaires d’apatite. Ce gîte a une zonation chimique verticale, qui aurait été produite par des gradations chimiques lors de la météorisation. La partie haute du gîte contient de la strengite, de l’Al-strengite et de la Fe-variscite jaunâtres ; les niveaux intermédiaires contiennent de la variscite verdâtre et les niveaux plus profonds, de la variscite verte. Les teneurs en Fe sont très basses dans les variscites vertes, de même que les valeurs de Cr et de V. Les spectres Raman de la variscite de Gavà présentent de petites différences avec ceux des autres variscites du monde, mais dans le gîte de Gavà on trouve aussi des variations dans les spectres Raman de variscite de chaque couleur. Donc, si on peut avoir une bonne base de données, la spectroscopie Raman présente non seulement un intérêt pour la discrimination en terme de provenance géographique d’un échantillon de variscite, mais aussi pour en déterminer la position au sein d’un gîte donné. Mots-clés : variscite, Raman, microsonde, filons, supergénétique

Kaolin deposits has been for long exploited in several regions of Angola, and some of the most important are produced by weathering of anorthositic rocks from the Cunene complex. However, a systematic research has not been carried out until the present mo Kaolin deposits has been for long exploited in several regions of Angola, and some of the most important are produced by weathering of anorthositic rocks from the Cunene complex. However, a systematic research has not been carried out until the present mo Kaolin deposits has been for long exploited in several regions of Angola, and some of the most important are produced by weathering of anorthositic rocks from the Cunene complex. However, a systematic research has not been carried out until the present mo

Kaolin deposits has been for long exploited in several regions of Angola, and some of the most important are produced by weathering of anorthositic rocks from the Cunene complex. However, a systematic research has not been carried out until the present moment. Some extensive outcrops of kaolinitic weathering proiles developed on Precambrian granitic rocks were discovered during a recent trip in the Caluquembe area, in the Huila province (SSE of Luanda). The present study determined the mineralogical features and thermal properties of the clay minerals fromthese outcrops. The mineral composition was determined by means of X-ray diffraction, Raman spectroscopy and scanning electron microscopy. The quantitative mineral phase analyses of the samples were obtained by X-ray diffraction proile reinement using Topas V2.2. The thermal behaviour was studied by differential thermal and thermogravimetric analysis. Whole-rock geochemical analyses on random powders (XRPD) reveal that samples are mainly composed of kaolinite, quartz, feldspars (e.g. albite and microcline) and muscovite. In addition, smectite and hematite have been detected only in some samples. The obtained results indicate that samples present high kaolinite contents (~85 wt%), although a few samples which contain smectite have lower percentages of kaolinite (~28% wt%). Thermal analyses were carried out to check the quantitative results of mineral phasesby XRPD. The differential thermal analysis (DTA) curve showsonly an endothermic peak at about 540 °C in dry air which conirms the dehydration of kaolinite [1] in samples lacking smectite. Mass loss in the samples, measured by thermogravimetric analysis (TG), is between 4 to 11 wt% until 650 ºC; samples with higher kaolinitecontents show the highest mass loss values. The amount of kaolinite calculated by mass loss is between 90 and 25 wt%. We can conclude that XRPD and TG results have a good correlation and the combination of both techniques is suitable to determine the kaolinite content in this kind of clay deposits. Based on the high content of kaolinitefrom the deposit of Caluquembe, this area is very suitable for the exploration and potential exploitation of kaolinite, which is a very valuable raw material demanded in the fabrication of ceramics, cosmetics, paper or pharmaceutical products.