Search Results (66)

The present study is part of the Horizon Europe-START project, which aims to recover tetrahedrite-group minerals present in mine dumps to be used as raw materials for the manufacture of thermoelectric devices. The aim of this work is to identify the mining waste facilities selected in Spain for the recovery of tetrahedrite and to outline the mineral processing operations performed on samples from each site to separate and concentrate this mineral. Ore deposits across Spain were selected based on the potential presence of tetrahedrite in their mining waste. A total of five deposits have been sampled, at which subsequent mineral separation and concentration tests have been conducted. A separation flowsheet is proposed in order to extract a high-purity tetrahedrite concentrate. Experimental results indicate two distinct options for separation approaches, depending on a key parameter that proves decisive in the processing of this mineral, which is whether the mineral paragenesis includes siderite. This study has demonstrated the technical feasibility of concentrating minerals of the tetrahedrite group through simple, cost-effective physical separation techniques—specifically magnetic and gravity separation—where the liberation size of the tetrahedrite exceeds 0.063 mm. Full article

The thermoelectric properties of skinnerite Cu₃SbS₃ and wittichenite Cu₃BiS₃ prepared by mechanochemical synthesis in a planetary ball mill from elemental precursors were investigated for the first time. X-ray diffraction (XRD) analysis of skinnerite after heat treatment revealed not only the presence of monoclinic skinnerite phase but also the presence of tetrahedrite phases. XRD analysis of wittichenite after both heat treatment and spark plasma sintering (SPS) revealed the presence of only the prepared orthorhombic wittichenite, whereas, in the case of skinnerite, not only skinnerite but also tetrahedrite is present after SPS treatment. The thermal stability of mechanochemically synthesized Cu₃SbS₃ and Cu₃BiS₃ samples was investigated by thermal analysis, which confirmed that Cu₃SbS₃ is thermally stable up to 604 K and Cu₃BiS₃ up to 550 K, respectively. Thermoelectric (TE) potential was evaluated by measuring the Seebeck coefficient, electrical and thermal conductivity, and figure of merit ZT. The performed thermoelectric (TE) measurements revealed a figure of merit ZT of 0.69 and 0.09 at 575 K for pristine skinnerite and wittichenite, respectively, sintered by SPS. The combination of mechanosynthesis followed by SPS allows for the preparation of materials that display a promising thermoelectric response. This approach opens up new possibilities for enhancing the thermoelectric properties of materials, which could have significant implications for various applications, such as energy conversion and waste heat recovery. Further research in this area is necessary to fully explore and exploit the potential of these materials for thermoelectric applications. Full article

Non-stoichiometric skinnerite Cu_3+mSbS₃ (−0.04 ≤ m ≤ 0.04) was synthesized via mechanical alloying and hot pressing. A phase analysis, microstructural characterization, and thermoelectric property evaluation were conducted to investigate the effects of Cu deficiency and excess. An X-ray diffraction of the mechanically alloyed powders confirmed the formation of cubic skinnerite, while the hot-pressed Cu-rich samples contained a secondary phase, identified as cubic tetrahedrite (Cu₁₂Sb₄S₁₃). The lattice constant decreased within the range of 1.0341–1.0347 nm for the non-stoichiometric compositions. The microstructural analysis revealed a skinnerite matrix with tetrahedrite inclusions in the Cu-excess samples. The differential scanning calorimetry showed a single endothermic peak at 876 K for the stoichiometric skinnerite, corresponding to its melting point, whereas the non-stoichiometric samples exhibited additional phase transitions at 814–818 K, and a melting reaction at 873–874 K. The electrical conductivity increased with the temperature, indicating non-degenerate semiconductor behavior. Between 323 and 423 K, the electrical conductivity varied depending on the Cu deficiency or excess, but above 423 K, all the non-stoichiometric samples exhibited higher electrical conductivity than the stoichiometric skinnerite. A positive Seebeck coefficient confirmed p-type conduction in all the samples, while Cu deficiency led to a decrease in the Seebeck coefficient but enhanced the power factor, due to increased electrical conductivity. The Cu_2.98SbS₃ sample exhibited the highest power factor of 0.85 mWm⁻¹K⁻² at 623 K. Although Cu deficiency resulted in increased thermal conductivity due to a higher carrier concentration, the significant enhancement in the power factor led to a maximum dimensionless figure of merit (ZT) of 0.59 at 623 K for Cu_2.98SbS₃, surpassing the ZT of 0.51 for the stoichiometric Cu₃SbS₃. Full article

There are a large number of fahlores recognized in the Zijinshan ore field, including tetrahedrite, tennantite, Zn-rich tetrahedrite, goldfieldite, Bi-rich tetrahedrite, etc. The changes in their mineral composition have significance for the evolution of the ore-forming environment. This article presents a detailed study of the fahlores using electron probe analysis. The results indicate that in the Zijinshan Au-Cu deposit, fahlores are Te-rich in shallow zones and Zn-rich in deep zones. The Zijinshan Xi’nan deposit is generally Zn-rich, with a Bi-rich in middle levels. The Longjiangting deposit is Sb- and Zn-rich in shallow zones and As- and Bi-rich in deep zones, whereas the Yueyang deposit is Sb- and Zn-rich in shallow zones and Bi-rich in deep zones. The fahlores in the Zijinshan ore field often show zoning in backscattered images due to As and Sb variations. From the porphyry to high-sulfidation stages, fahlores evolve from Fe-rich to Zn-, Bi-, and Sb-rich, and finally to Te-rich. From the porphyry to low-sulfidation stages, fahlores transition from Bi-rich to Zn-rich and eventually to Ag-rich compositions. The discovered mineral assemblages of the fahlores are of great significance for understanding the framework of complex porphyry shallow hydrothermal environments and prospecting for underlying porphyry ore bodies in the Zijinshan ore field. Full article

Thermoelectric materials have considerable potential in the mitigation of the global energy crisis, through their ability to convert heat into electricity. This study aims to valorize natural resources, and potentially reduce production costs, by incorporating tetrahedrite–tennantite (td) ores from the Portuguese Iberian Pyrite Belt into synthetic samples. The ore samples were collected in a mine waste at Barrigão and as “dirty-copper” pockets of ore from the Neves Corvo mine. Subsequently, high-energy ball milling and hot pressing were employed in the production of thermoelectric materials. These are characterized by XRD, SEM/EDS, and thermoelectrical properties. The complete dissolution of the dump material sulfides with the synthetic tetrahedrite constituents led to an increase in the amount of the tetrahedrite–tennantite phase, which was made up of a tetrahedrite–tennantite–(Fe) solid solution. The thermoelectric characterization of these materials is provided, revealing that most of the combined synthetic ore samples displayed better results than the pristine tetrahedrite, mostly due to higher Seebeck coefficient values. Furthermore, the best thermoelectric performance is achieved with 10% of ore, where a power factor of 268 µW.K⁻².m⁻¹ is reached at room temperature. Full article

A possible thermodynamic study of processing Cu (Ag, Au) and Fe sulfide concentrate as a by-product after the processing of tetrahedrite concentrate, applying pyrometallurgical and hydrometallurgical methods, was studied. The sample of sulfide concentrate, 34.7 wt. % Cu, 21.4% Fe, 12 g/t Au, and 7.317 g/t Ag was contained. Analytical technique AAS was used to analyze the sample before conducting a thermodynamic study of the leaching of sulfide concentrate by applying Pourbaix Eh–pH diagrams. The outcome of this thermodynamic research will provide essential data to support recent hydrometallurgical technologies. If its correctness can be verified experimentally, this result will be promoted to developing a new alternative copper-production technology. The minor components Sb, As, Hg, and Bi are also present in the concentrate in the form of sulfides Sb₂S₃, As₂S₃, Bi₂S₃, and HgS. This theoretical proposed hydrometallurgical technology shows that it is possible to obtain Fe in the form of Fe(OH)₃, and after its thermal decomposition, it can be prepared as Fe₂O₃ as a marketable product. In any case, the most economically advantageous would be complete hydrometallurgical processing, i.e., also Cu(Ag,Au)Fe sulfide concentrate, with the possibility of valorizing Cu, Ag, and Au in metallic form. Full article

Thermoelectric (TE) materials offer a promising solution to reduce green gas emissions, decrease energy consumption, and improve energy management due to their ability to directly convert heat into electricity and vice versa. Despite their potential, integrating new TE materials into bulk TE devices remains a challenge. To change this paradigm, the preparation of highly efficient tetrahedrite nanocomposites is proposed. Tetrahedrites were first prepared by solid state reaction, followed by the addition of MoS₂ nanoparticles (NPs) and hot-pressing at 848 K with 56 MPa for a duration of 90 min to obtain nanocomposites. The materials were characterized by XRD, SEM-EDS, and Raman spectroscopy to evaluate the composites’ matrix and NP distribution. To complement the results, lattice thermal conductivity and the weighted mobility were evaluated. The NPs’ addition to the tetrahedrites resulted in an increase of 36% of the maximum figure of merit ($zT$) comparatively with the base material. This increase is explained by the reduction of the material’s lattice thermal conductivity while maintaining its mobility. Such results highlight the potential of nanocomposites to contribute to the development of a new generation of TE devices based on more affordable and efficient materials. Full article

This study considers the features of the chemical composition, internal structure, and oscillatory zoning of sulfosalts and sulfates in the epithermal high–intermediate-sulfidation-type Au-Ag-Te Emmy deposit (Khabarovsk Territory, Russia). In Emmy deposit, sulfosalts primarily represent goldfieldite, probably corresponding to a high-sulfidation (HS) mineral association replaced bytennantite–tetrahedrite group minerals. The latter is associated with tellurides and native tellurium, corresponding to an intermediate-sulfidation (IS)-type ore assemblage and suggesting an increasing influx of Te, Sb, and As in the system. Goldfieldite is replaced by native tellurium and tellurides along its growth zones, and is characterized by oscillatory zoning. The replacement of goldfieldite by mercury, nickel, lead, and copper tellurides indicate a new influx of native gold, native tellurium, and gold–silver tellurides into the open mineral-forming system. At deeper levels of the Emmy deposit, an advanced argillic alteration assemblage includes aluminum phosphate–sulfate (APS) minerals, represented by members of the svanbergite–woodhouseite series. Element mapping of the studied APS mineral grains indicated three distinct areas recording the evolution of the hydrothermal system in the Emmy: an oscillatory-zoned margin enriched in sulfur, lead, and barium, corresponding to the late influx of IS state fluids related to gold and tellurides; an intermediate part, which is leached and corresponds to the HS mineralization stage; and the central part of the grains, which is enriched in cerium, calcium, and strontium, resulting from a replacement of magmatic apatite in the pre-ore alteration stage. The leached zone between the core and rim of the APS grains is related to a change in crystallization conditions, possibly due to the mixing processes of the fluids with meteoric water. Barite, found in the upper level of the advanced argillic hypogene alteration assemblage, is also characterized by oscillatory zoning, associated with the enrichment of individual zones in lead. Micron gold particles associated with barite are confined to their lead-enriched zones. The study of fluid inclusions in quartz within the Emmy deposit showed the hydrothermal ore process at a temperature of 236–337 °C. Homogenization temperatures for quartz–pyrite–goldfieldite mineral association vary within 337–310 °C and salinity varies within 0–0.18 wt.%NaCl equivalent, and for gold–silver–telluride–polymetallic mineral association, they decrease and vary within 275–236 °C and salinity slightly increases from 0.18 to 0.35 wt.%NaCl equivalent. This study demonstrates that the nature of oscillatory zoning in sulfosalts and sulfates in the Emmy deposit results from an external process. Such a process is of fundamental importance from a genetic point of view. Full article

The Alattu–Päkylä gold occurrence is located in the Northern Lake Ladoga area, in the Raaha-Ladoga suprasubduction zone, at the Karelian Craton (AR)—Svecofennian foldbelt (PR₁) boundary. Its gold ore mineral associations are of two types of mineralization: (1) copper–molybdenum–porphyry with arsenopyrite and gold (intrusion-related) and (2) gold–arsenopyrite–sulfide in shear zones. Optical and scanning electron microscopy, X-ray fluorescence spectrometry, inductively coupled plasma mass spectrometry (ICP-MS), instrumental neutron activation analysis (INAA) and fire analysis with AAS finishing were used to study them. Type 1 was provoked by shallow-depth tonalite intrusion (~1.89 Ga) and type 2 by two stages of Svecofennian metamorphism (1.89–1.86 and 1.83–1.79 Ga) with the possible influence of the impactogenesis of the Janisjärvi astrobleme (age ~1 Ga). Intrusive and host rocks were subjected to shearing accompanied by the formation of ore-bearing metasomatic rocks of the propylite-beresite series (depending on substrate) and quartz–sericite, quartz and sericite–tourmaline veins and streaks. Ore mineralization is present as several consecutive mineral associations: pyritic–molybdenite with arsenopyrite and gold; gold–arsenopyrite; quartz–arsenopyrite with antimony sulfosalts of lead; gold–polysulfide with tetrahedrite –argentotetrahedrite series minerals and gold–antimony with Pb–Sb–S system minerals and native antimony. Arsenopyrite contains invisible (up to 234 ppm) and visible gold. Metamorphosed domains in arsenopyrite and rims with visible gold around it are usually enriched in As, indicating higher (up to >500 °C) temperatures of formations than original arsenopyrite with invisible gold (<500 °C). A paragenetic sequence associated with the deposition of invisible and visible gold established at the Alattu–Päkylä ore occurrence: pyrrhotite + unaltered arsenopyrite (with invisible gold) → altered arsenopyrite (As-enriched) + pyrite ± pyrrhotite + visible gold. Gold, associated with gudmundite, sphalerite and native antimony, seems to be due to cainotypic rhyodacitic porphyry cutting tonalite intrusion or with a retrograde stage in post-Svecofennian metamorphism. The isotopic composition of Pb and ²³⁸U/²⁰⁴Pb (9.4–9.75) for the feldspar of the tonalite intrusion and the pyrite of gold mineralization, εNd (−4 up to −5) for tonalites and ẟ³⁴S values of −2.10–+4.99 for arsenopyrite, indicate the formation of gold occurrence provoked by Svecofennian magmatic and tectono-thermal processes with the involvement of matter from a mantle-lower crustal reservoir into magma formation and mineralization. Full article

The Václav vein (Březové Hory deposit, Příbram ore area, Czech Republic) is a base–metal vein containing minor Cu-Zn-Pb-Ag-Sb sulfidic mineralization in a usually hematitized gangue. A detailed mineralogical study using an electron microprobe revealed a complicated multistage evolution of the vein. Early siderite and Fe-rich dolomite were strongly replaced by assemblages of hematite+rhodochrosite and hematite+kutnohorite/Mn-rich dolomite, respectively. In addition, siderite also experienced strong silicification. These changes were associated with the dissolution of associated sulfides (sphalerite, galena). The following portion of the vein contains low-Mn dolomite and calcite gangue with Zn-rich chlorite, wittichenite, tetrahedrite-group minerals, chalcopyrite, bornite, and djurleite, again showing common replacement textures in case of sulfides. The latest stage was characterized by the input of Ag and Hg, giving rise to Ag-Cu sulfides, native silver (partly Hg-rich), balkanite, and (meta)cinnabar. We explain the formation of hematite-bearing oxidized assemblages at the expense of pre-existing “normal” Příbram mineralization due to repeated episodic infiltration of oxygenated surface waters during the vein evolution. Episodic mixing of ore fluids with surface waters was suggested from previous stable isotope and fluid inclusion studies in the Příbram ore area. Our mineralogical study thus strengthens this genetic scenario, illustrates the dynamics of fluid movement during the evolution of a distinct ore vein structure, and shows that the low content of ore minerals cannot be necessarily a primary feature of a vein. Full article

The major issue associated with thermoelectric performance is the low efficiency of power conversion. The main challenge is achieving a combination of high Seebeck coefficient, high electrical conductivity, and low thermal conductivity for a significantly improved figure of merit (ZT). Developing strategies include the production of tetrahedrites with an intrinsically low thermal conductivity through the solvothermal method, using a low reaction time and processing temperature. Here, we report on the preparation of Cu-rich tetrahedrites through the solvothermal technique at low temperature, providing a promising strategy for the preparation of materials with potential applications in thermoelectricity. The influence of synthesis reaction time and temperature on the morphological, structural, and thermoelectrical properties of the samples was investigated through different characterization techniques. Tetrahedrite synthesized at 180 °C for 19 h yielded a favorable ZT value of >0.43 and a thermal conductivity of 0.2 Wm⁻¹ K⁻¹ (423 K), related to the Sb³⁺/Sb⁵⁺ and Cu⁺/Cu²⁺ ratio, as was observed by XPS. The cubic tetrahedrite phase attributed to the (222) plane was confirmed by XRD and TEM and the intense Raman mode observed at 351 cm⁻¹. SEM images revealed that nanotetrahedral Cu-rich tetrahedrites efficiently assemble into spherical structures, resulting in an improvement in the Seebeck coefficient (437 µVK⁻¹) and electrical conductivity. Full article

A calc–alkaline dioritic–andesitic–dacitic intrusive–volcanic complex of Early Oligocene (30 Ma) age and its Mesozoic sedimentary basement at Recsk host a well-preserved porphyry–skarn–polymetallic carbonate-replacement–epithermal mineral system. The unique occurrence offers an exceptional possibility to study these related mineralization types at a single locality. This study presents the textural–paragenetic, compositional characteristics, and systematics of sulfide mineral assemblages for the porphyry, skarn, and carbonate-replacement ore types, which are currently situated at a depth of 500–1200 m below the present surface. Detailed petrography combined with EPMA analyses of molybdenite, galena, sphalerite, tetrahedrite-group minerals and Bi-bearing sulfosalts allows for the establishment of characteristic mineral and chemical fingerprints for each mineralization type. Rhenium concentration in molybdenite, occurring as rare disseminations and quartz–carbonate veinlets in altered host rocks in all three mineralization types, shows a decreasing trend towards the more distal mineralization types. High Re contents ($\overline{\mathrm{x}}$ = 1.04 wt.%, max. up to 4.47 wt%) are typical for molybdenite from the porphyry mineralization, but Re is not homogeneously distributed, neither within individual molybdenite crystals nor on a mineralization scale. Copper and Se show opposite behavior in molybdenite, both becoming enriched in the more distal mineralization types. Silver, Bi, and Se concentrations increase in galena and tetrahedrite-group minerals, both towards the country rocks, making them the best candidates for vectoring within the whole hydrothermal system. For tetrahedrite-group minerals, Ag, Bi, Se, together with Sb and Zn, are the suitable elements for fingerprinting; all these are significantly enriched in the distal carbonate-replacement mineralization compared to the other, more proximal ore types. Additionally, further trends can be traced within the composition of sulfosalts. Lead-bearing Bi sulfosalts preferentially occur in the polymetallic carbonate-replacement veins, while being under-represented in the skarn and porphyry mineralization. Porphyry mineralization hosts Cu-bearing Bi sulfosalts dominantly, while skarn is characterized by Bi-dominated sulfosalts. Sphalerite, although present in all mineralization types, cannot be used for fingerprinting, vectoring, or thermobarometry based on EPMA measurements only. Trace element contents of sphalerite are low, often below the detection limits of the analyses. This is further complicated by the intense “chalcopyrite disease” occurring throughout the distal mineralization types. All the above-listed major, minor, and trace element ore mineral characteristics enable the characterization of the Recsk ores by mineral geochemical fingerprints, providing a possible vectoring tool in porphyry Cu–(Mo)–Au-mineralized systems. Full article

The concealed Molai Zn-Pb±(Ag,Ge) stratiform deposit in southeastern Peloponnese is hosted in Triassic intermediate tuffs, ignimbrites and subaerial andesitic flows. The host rocks display trace element signatures of a Supra-Subduction Zone (SSZ) setting. Three ore-forming stages are recognized, with stages I and II related to formation of the epigenetic, stratiform, massive-to-semi-massive ore and a late stage III associated with vein-type mineralization. The O and D isotope geochemistry of gangue chlorite and epidote reveal mixing with fresh meteoric water during the weaning stages of the hydrothermal activity of the late stage II due to uplifting of the hydrothermal system. Sphalerite is the major ore phase, with three different varieties formed during stages I (Sp-I) and II (Sp-II and Sp-III). All sphalerite varieties coexist, depicting gradual change in the chemistry of the ore-forming fluids. Molai ores are characterized by elevated Ag and Ge contents. Tetrahedrite is the major Ag carrier, while among the three sphalerite varieties, early Sp-I comprises the highest Ge contents. The Molai Zn-Pb±(Ag,Ge) deposit is characterized by intermediate features between bimodal felsic massive sulfides and subaerial epithermal systems based on the shallow formation depth, the presence of hydraulic breccias associated with phase separation, the ore formation along high-angle faults, the relatively low ore-forming temperatures below 250 °C obtained from geothermometry, and the absence of the typical structure of bimodal felsic type ores. Full article

The Bou Dahar Pb-Zn district, located in the Moroccan High Atlas, is a typical carbonate-hosted Pb-Zn ore district (>30 Mt at 4 wt.% Pb, 4 wt.% Zn). In situ trace element analysis was performed using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) on galena and cerussite from different ore types. The galena is generally enriched in Ag and Sb, secondarily enriched in Cu, with a trace amount of Cd and As, but extremely depleted in Bi and Tl. The main substitution mechanism in galena is (Ag, Cu)⁺ + Sb³⁺ ↔ 2Pb²⁺, and at high Sb concentrations, the further substitution of 2Sb³⁺ + □ ↔ 3Pb²⁺ (where □ represents a vacancy) took place. Micro-inclusions of Cu-Sb-bearing minerals (such as tetrahedrite) and Ag-bearing minerals (such as acanthite) may exist in some situations. The features of trace elements in galena show the existence of different coupled substitutions in vein-related ore, breccia-related ore, and strata-bound ore. This suggests that the Bou Dahar district experienced multistage mineralization. The MVT model alone cannot fully explain the ore-forming process. The cerussite replacing strata-bound galena is enriched in Sr, Ba, Ag, and Cu, with minor Sb, As, and Tl. Strontium and Ba are directly substituted with Pb in the cerussite lattice. Copper and Ag are likely present in cerussite as nano-inclusions, which differs from the coupled substitution mechanism of the original galena. High concentrations of Ag may occur due to minor electrum inclusions. The enrichment of Ag, Cu, and Au in cerussite during the oxidation process may guide the optimization of ore processing, especially in extracting valuable trace/minor elements. Full article

The Biche-Kadyr-Oos epithermal Au-Ag ore occurrence is a prospective object in the Ak-Sug porphyry copper ore cluster (Eastern Sayan) in the northern part of the Central Asian orogenic belt (CAOB). The mineralization consists of gold-sulfide-quartz and gold-polysulfide-carbonate-quartz veins with argillic zones in the Lower Cambrian volcanic-sedimentary rocks. The origin of the Au-Ag ore occurrence is still debatable. To determine the origin, we examined the mineralogical and geochemical features, conditions of formation, and fluid sources of the Biche-Kadyr-Oos ore. A mineralogical and geochemical investigation outlines three stages of mineral formation: early argillic stage; gold-sulfide-quartz stage with pyrite, marcasite, pyrrhotite, arsenopyrite, chalcopyrite, less frequently sphalerite, hessite, gold, and electrum; and late gold-polysulfide-carbonate-quartz stage with gold, electrum, Hg-electrum, Se-acanthite, Se-galena, bornite, tennantite, tetrahedrite, hessite, tellurobismuthite, bismuthinite, matildite, jamesonite, ourayite, native Bi, and barite. Fluid inclusion study (thermometry, Raman spectroscopy) in quartz and mineral thermometry (electrum and sphalerite paragenesis) determined that ore veins were formed at P~0.5 kbar from CO₂-water Na-K-chloride fluid (4.9–9.6 wt % NaCl eqv) and temperatures from 300 to 200 °C (early gold-sulfide-quartz veins at 300–230 °C, and late gold-polysulfide-carbonate-quartz veins at 290–200 °C) and variations in fO₂, fS₂, fSe₂ and fTe₂. The S isotopic composition in sulfides and δ³⁴SH₂S values of the fluid are +1.3‰ and +4.7‰, respectively, (T = 300–275 °C) indicating magmatic S in ore formation. The oxygen isotope data indicate that during the formation of veins, the magmatic fluid mixed with meteoric water (δ¹⁸O_fluid is from +3.4 to +6.4‰). The isotopic data that were obtained combined with mineralogical and geochemical features and conditions of ore formation indicate the similarity of Biche-Kadyr-Oos ore occurrence with epithermal Au-Ag deposits of intermediate sulfidation (IS) type. The presence of epithermal Au-Ag mineralization of the Biche-Kadyr-Oos IS type in ore cluster of the Ak-Sug Cu-Au-Mo porphyry deposit indicates the existence of a single porphyry-epithermal ore-magmatic system. Full article