Mines i minerals de la serra de les Ferreres. Les mines de Rocabruna, Bruguers, Gavà, el Baix Llobregat, Catalunya.
Abstract and Figures
Les Ferreres range (Gavà, Barcelona, Catalonia) has seen several cultures and empires pass through the millennia. Since the Neolithic, its entrails have been mined in search of the men they hide. In the Neolithic period, variscite was the mineral that moved the miners to open galleries and trenches. Later, those who knew the secret of iron production opened up the earth looking for minerals such as goethite, iron ochres (limonite) or hematite. Behind them, the Roman Empire continued the extraction of precious minerals. And in the Middle Ages and the modern age, the iron of these regions continued to be appreciated. Until the sixties of the 20th century, the mines worked when the price of the ore allowed it.
But in addition to this rich mining heritage, this mountain range and its mines and outcrops have provided numerous mineral species, some appreciated by mineralogists from all over the world... They have also expanded our mineralogical heritage.
In this book you are holding in your hands you will find a collection of mining history and a description of this exceptional mineralogy. It is the result of the research carried out by the Grup Mineralògic Català in recent years, with the collaboration of Geociències Barcelona (GEO3BCN-CSIC), the Museu de Ciències NAturals de Barcelona and the support of the Universitat de Barcelona.
Sharing experiences with the people of the region, historical research, field work and scientific curiosity have been the engines that have pushed us to carry out this work.
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In the Neolithic Gavà mines, variscite and turquoise were exploited for ornaments manufacturing, although some prospective pits and tunnels were dug on other similar greenish minerals such as smectite or kandite. A 3D study of the distribution of mineral phases allows us to determine the parameters involved in variscite colours. Methods are comprised of quantitative colourimetry, thin section petrography, SEM-BSE-EDS, EMPA, XRD, Raman spectroscopy, and 57Fe Mössbauer spectrometry. Mapping of the mines indi-cates that colour is not directly dependent on depth. Although variscite from Gavà is poor in Cr3+ and V+3 compared with gemmy variscite from other localities, the deep green samples content has the highest values of Cr3+. In the case of cryptocrystalline mixtures with jarosite, phosphosiderite, or goethite, variscite tends to acquire a greenish brown to olivaceous hue. If white minerals such as quartz, kandite, crandallite, or alunite are involved in the mixtures, variscite and turquoise colours become paler.
The essential role of Critical Elements (CE) in 21st century economy has led to an increasing demand of these metals and promotes the exploration of non-conventional deposits such as weathering profiles. The present work is focused on the study of a weathering profile located at the Archaeological Park of the Gavà Neolithic Mines, Barcelona, Catalonia, Spain. In the Gavà deposit, acid and oxidising meteoric fluids generated intense weathering during the early Pleistocene, affecting series of Llandoverian black shales and associated syn-sedimentary phosphates. The circulation of these acid fluids at deeper levels of the profile generated supergene vein-like mineralisations comprised of secondary phosphates (e.g., variscite, perhamite, crandallite, phosphosiderite) and sulphates (e.g., jarosite, alunite). This supergene mineralisation is significantly enriched in certain CE (e.g., Ga, Sc, REE, In, Co and Sb) that were mobilised from host rock components and later hosted in the crystal lattice of supergene minerals. Weathering processes and corresponding supergene enrichment of CE at the Gavà deposit could be used as an example to determine exploration guidelines of CE in weathering profiles and associated supergene phosphates worldwide.
Barremian-Bedoulian flint from the Vaucluse region (western Provence, SE France), is traditionally considered one of the most significant chrono-cultural markers of the Chasséen culture during the Middle Neolithic (end of the 5th and beginning of the 4th millennium BC). Diffusion of Provençal flints became massive during the first half of the 4th millennium BC, penetrating in several neighbouring cultural spheres such as the Sepulcros de Fosa culture in north-eastern Iberia. The integrated study of the lithic assemblages from the variscite mines of Gavà (Barcelona) and its contextualization within the Sepulcros de Fosa culture in north-eastern Iberia have revealed unexpected complexity in the modes of consumption, use and status of imported Barremian-Bedoulian industries in north-eastern Iberia during the 5th to 4th millennia cal. BC transition. Local communities within this region, already controlling extraction and regional diffusion of variscite ornaments, exerted control over the fluxes of Vauclusian flint south of the Pyrenees, where it had a triple status (functional, symbolic and both). In addition, the results provide complementary data to better understand relevant aspects of the nature and organisation of Barremian-Bedoulian flint exploitation and early supply systems at the Provençal producing sites during the later phase of the Chasséen culture.
RESUMEN La minería de los recursos de hierro del área de Gavà (Cataluña) fue activa de forma intermitente durante las épocas Ibérica y Romana, la Edad Media, y hasta la era industrial, lo cual se ha probado mediante datos arqueológicos y documentos históricos. Es posible que, inclusive, la minería de hierro en el área haya existi-do durante el periodo Neolítico. Las mineralizaciones de hierro se formaron en dos estadios: (1) alteración hidrotermal regional asociada a cabalgamientos Her-cínicos que produjo ankeritizaciones de calizas en las series del Paleozoico, y (2) el reemplazamiento kárstico de los carbonatos ricos en hierro durante el Plioceno y el Cuaternario por medio de fluidos supergénicos que pro-dujeron ocres con goethita y hematites. El estilo de mine-ralización depende en gran medida de las características del protolito reemplazado, lo cual lleva a la definición de tres estilos de mineralización: (1) El reemplazamiento supergénico de calizas masivas ankeritizadas del Pri-doliense produjo únicamente reemplazamientos locales restringidos a discontinuidades estructurales o estrati-gráficas por lo tanto, las mineralizaciones son de dimen-siones reducidas en forma de vetillas o masas verticales irregulares; (2) El reemplazamiento de alternancias de calizas ankeritizadas con pizarras que contienen pirita diseminada (Lockoviense) produjo bolsadas de minera-lizaciones masivas ricas en sílice derivadas de las piza-rras alteradas; (3) El reemplazamiento de carbonatos cabalgados por pizarras ricas en sulfuros y fosfatos fa-voreció la formación de mineralizaciones estratoligadas masivas, que son las de mayor tamaño y grado en el área de estudio, pudiendo estar localmente enriquecidas en minerales del supergrupo de la alunita y en fosfatos de Ca y Fe. Afloramientos de todos estos estilos de mi-neralización fueron explotadas tanto en la antigüedad como en la Edad Media, aprovechando la alta calidad metalúrgica de las menas, pese a que los dos primeros estilos de mineralización presentan cuerpos de reducido tamaño. Por ello, en dichas épocas la explotación fue artesanal mediante trincheras o pocillos. En cambio, en la época industrial sólo se beneficiaron los recursos ma-sivos del tercer estilo de mineralización a cielo abierto y a través de galerías. ABSTRACT 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 an-keritization 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 proto-lith, 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 an-keritized 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.There-fore, 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.
Fanfaniite, Ca 4 Mn 2+ Al 4 (PO 4) 6 (OH,F) 4 Á12H 2 O, is a new secondary phosphate mineral from the Foote spodumene mine, North Carolina, USA and the Hagendorf-Süd pegmatite, Bavaria, Germany. At the Foote mine, it forms radial aggregates up to 0.5 mm in diameter of colourless, transparent, thin blades, flattened on {010} and elongated on [001], associated with whiteite-(CaMnMn). At Hagendorf-Süd, the mineral occurs as isolated very thin laths on the surface of fibrous spheroids of kayrobertsonite and is associated with altered triplite-zwieselite and whiteite-(CaMnMn). The measured density (Foote mine) is 2.58(2) g cm À3. Optically, fanfaniite (Foote mine) is biaxial (-), with a = 1.573(2), b = 1.582(2), c = 1.585(2) and 2V(meas) = 57(1)°. Dispersion was not observed. The optical orientation is: Z = b, X ^ c % 40° in b obtuse. Pleochroism was not evident. Electron microprobe analyses gave the empirical formulas Ca 3.91 Mn 2þ 0:77 Mg 0.10 Zn 0.02 Al 3.89 Fe 3þ 0:21 (PO 4) 6 (OH) 3.90 (H 2 O) 12.10 (Foote mine) and Ca 3.73 Mn 2þ 0:76 Mg 0.25 Zn 0.08 Al 3.89 Fe 3þ 0:29 (PO 4) 6 F 1.10 (OH) 3.08 (H 2 O) 11.82 (Hagendorf-Süd). Fanfaniite has monoclinic symmetry, space group C2/c, with a = 10.021(4) Å, b = 24.137(5) Å, c = 6.226(3) Å, b = 91.54(2)° and V = 1505(1) Å 3. The crystal structure was refined to R obs = 0.043 for 1909 unique reflections to a resolution of 0.7 Å. Fanfaniite is the Mn 2+-dominant analogue of montgomeryite. The name honours Luca Fanfani who structurally characterised many phosphate minerals including montgomeryite.
The calcioferrite group has been formally approved by the Commission on New Minerals, Nomenclature and 13 Classification of the International Mineralogical Association (proposal 19-B). It comprises four minerals with C-centred monoclinic 14 cells and general formula Ca 4 A 2+ B 3+ 4 (PO 4) 6 (OH) 4 Á12H 2 O, where A and B = Mg and Fe for calcioferrite, Mg and Al for 15 montgomeryite, Mn and Fe for zodacite and Mn and Al for fanfaniite, together with the triclinic mineral kingsmountite, Ca 3 Mn 2+ Fe 2+ 16 Al 4 (PO 4) 6 (OH) 4 Á12H 2 O. The minerals with B = Fe form the calcioferrite subgroup and those with B = Al form the montgomeryite 17 subgroup.The triclinic member was recently approved as the mineral "aniyunwiyaite" (IMA2018-054). New measurements on the 18 holotype specimen of kingsmountite, however, show that it has the same crystallographic and chemical properties as "aniyunwiyaite" 19 and, consequently, "aniyunwiyaite" has been discredited as being kingsmountite. Kingsmountite is triclinic, PÀ1, with a = 20.067(6) Å, 20 b = 13.197(4) Å, c = 6.255(3) Å, a = 89.35(2)°, b = 91.21(2)°, c = 112.20(2)°, V = 1533.4(10) Å 3 and Z = 2. The structure was 21 solved and refined to R obs = 0.059 for 4351 reflections with I > 3r(I). The crystal structure is a superstructure of the C-centred 22 monoclinic montgomeryite structure, having a doubled a m cell parameter. The superstructure results from ordering of octahedrally 23 coordinated Mn in one of four independent 8-coordinated Ca sites, and ordering of A site cations, which in the 24 Ca 4 AB 4 (PO 4) 6 (OH) 4 Á12H 2 O minerals are statistically distributed over half-occupied sites. 25
The crystal structures of the secondary ferric iron minerals kamarizaite, Fe33+(AsO4)2(OH)3 · 3H2O, and tinticite, Fe33+(PO4)2(OH)3 · 3H2O, for which highly contradictory data on crystal symmetry were reported, were studied by a combination of single-crystal X-ray diffraction and Rietveld refinement (supplemented by chemical analyses and thermogravimetry), using type material of both species and additional samples from several other localities, including the type localities. The previously unknown crystal structure of kamarizaite was determined from single-crystal intensity data (MoKα, 293 K, R(F) = 2.91 %; all H atoms detected) using a sample from the Le Mazet vein, Échassières, Auvergne, France. The mineral is triclinic, space group P1 (no. 2), with a = 7.671(2), b = 8.040(2), c = 10.180(2) Å, α = 68.31(3), β = 75.35(3), γ = 63.52(3)°, V = 519.3(2) AR3, Z = 2. Rietveld analyses of fine-grained kamarizaite collected underground at two different spots in Lavrion, Greece (Hilarion and Jean Baptiste areas) confirmed the structure model. Rietveld analyses of fine-grained tinticite from Tintic, Utah (USA), Bruguers (Spain) and Weckersdorf (Germany) demonstrate that kamarizaite and tinticite are triclinic and isotypic. A previously published structure model for tinticite, as well as the originally reported orthorhombic symmetry for kamarizaite, are shown to be incorrect. Refined unit-cell parameters of acotype tinticite specimen from Tintic are: a = 7.647(1), b = 7.958(1), c = 9.987(1) Å, α = 67.90(1), β = 76.10(1), γ = 64.10(1)°, V = 504.4(2) Å. Bruguers and Weckersdorf tinticite have very similar parameters. The common atomic arrangement is characterised by three unique, octahedrally coordinated Fe sites (on which Fe may be partially replaced by minor Al), two unique tetrahedrally coordinated T (As or P) sites, eight O, three Oh, three Ow and nine H sites. The topology features zig-zag chains along [110] of dimers built of two edge-sharing FeO6 octahedra corner-linked by a third FeO6 octahedron. The chains are corner-linked by the TO4 tetrahedra thus establishing a mixed octahedral-tetrahedral framework with a T:Fe ratio of 0.67, a pronounced layered arrangement parallel to (001) and narrow channels along [010]. Medium-strong to weak hydrogen-bonds provide additional strengthening of the structure. The topology is closely related to that of the recently described, triclinic aluminium phosphate afmite.
Crystals of red montgomeryite associated with robertsite, whitlockite, englishite and several other species have been found at the Tip Top mine near Custer, South Dakota. Microprobe analysis gave CaO 19.1, MnO 0.5, MgO 3.5, Al 2O 3 17.1, P 2O 5 36.6, H 2O 23.2 (by diff.), = 100.0, which yields (Ca 3.97Mn 0.08) SIGMA 4.05Mg 1.01Al 3.89(PO 4) 6.00(OH) 4.06.12.94H 2O, based on 6 phosphorus atoms. Considering the excess of divalent cations and low Al content, some Mn may be present as Mn 3+, and might cause the red colour. The crystals have alpha 1.572, beta 1.579, gamma 1.582, 2V alpha 75o, r < v, with alpha :c approx +60o, gamma = b; pleochroism alpha light orange-brown, beta very pale magenta-pink and gamma very pale orange-brown. Based on chemical and X-ray data, calcioferrite is probably the Fe 3+ analogue of montgomeryite, and an inadequately described mineral from the Hagendorf pegmatite near Waidhaus, Bavaria, may be either a ferrian kingsmountite or a new member of the montgomeryite group with end-member formula 218Ca 4MnFe 43+(PO 4) 6(OH) 4.12H 2O.-G.W.R.