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This paper presents a thorough study of the main features and the decay causes and mechanisms of serpentinites both freshly quarried and after centuries exposure at the main façade of the sixteenth century Royal Chancery (Granada, Spain). In particular, the process of in situ formation of calcium and magnesium sulfates has been studied. Several decay factors are identified, all of them acting synergistically in the deterioration of slabs made of serpentinite. Among them, chemical weathering of sulfides such as pyrite present in the original serpentinite induces the formation of sulfate salts such as gypsum or epsomite, salts which are considered the main cause of decay. In addition, unsuitable restoration treatments involving the use of Portland cement to fill up cracks and surface lacunae, the polluted environment of the surrounding area, and the location of the slabs close to the ground, favoring capillary rise of water, all contributed to their deterioration. This work helps to gain knowledge on the deterioration process of ornaments made of serpentinite, allowing us to propose the most appropriate measures to guarantee their conservation.
R. Navarro; D. Pereira; E. Fernández de Arévalo; E.M. Sebastián-Pardo; C. Rodriguez-Navarro. Weathering of serpentinite stone due to in situ generation of calcium and magnesium sulfates. Construction and Building Materials 2021, 280, 122402 .
AMA StyleR. Navarro, D. Pereira, E. Fernández de Arévalo, E.M. Sebastián-Pardo, C. Rodriguez-Navarro. Weathering of serpentinite stone due to in situ generation of calcium and magnesium sulfates. Construction and Building Materials. 2021; 280 ():122402.
Chicago/Turabian StyleR. Navarro; D. Pereira; E. Fernández de Arévalo; E.M. Sebastián-Pardo; C. Rodriguez-Navarro. 2021. "Weathering of serpentinite stone due to in situ generation of calcium and magnesium sulfates." Construction and Building Materials 280, no. : 122402.
Fluorite is an important industrial mineral composed of calcium and fluorine (CaF2). This mineral is widely distributed through different deposits. However, in most cases, fluorite is tightly associated with gangue, such as calcite and quartz. In this paper, different depressants are tested in the flotation of fluorite in two different laboratory configurations—cell and column. Quebracho tree (QT) was tested as the main depressant in combination with white dextrin (WD), potato starch (PT), carboxymethyl cellulose (CMC), and sodium hexametaphosphate (SHMP). The optimum pulp pH of the flotation of fluorite was determined as approximately 9.5–10. The best results are obtained using a combination of quebracho and white dextrin as depressants, reaching 74% of fluorite grade for modified column flotation and 70.5% for cell flotation. Additionally, the metallurgical recovery obtained higher values when the flotation was carried out in the modified column and using the same combination of depressant agents—75% for modified column flotation and 60% for flotation cell.
J. R. Corpas-Martínez; A. Pérez; R. Navarro-Domínguez; C. Amor-Castillo; M. A. Martín-Lara; M. Calero. Comparison Between Performance of Fluorite Flotation Under Different Depressants Reagents in Two Pieces of Laboratory Equipment. Applied Sciences 2020, 10, 5667 .
AMA StyleJ. R. Corpas-Martínez, A. Pérez, R. Navarro-Domínguez, C. Amor-Castillo, M. A. Martín-Lara, M. Calero. Comparison Between Performance of Fluorite Flotation Under Different Depressants Reagents in Two Pieces of Laboratory Equipment. Applied Sciences. 2020; 10 (16):5667.
Chicago/Turabian StyleJ. R. Corpas-Martínez; A. Pérez; R. Navarro-Domínguez; C. Amor-Castillo; M. A. Martín-Lara; M. Calero. 2020. "Comparison Between Performance of Fluorite Flotation Under Different Depressants Reagents in Two Pieces of Laboratory Equipment." Applied Sciences 10, no. 16: 5667.
In this study, two new collectors for fluorite flotation DP-OMC-1033 (DP-I) and DP-OMC-1234 (DP-II) were tested and compared with oleic acid (OA), sodium oleate (SO) and potassium oleate (PO). According to fluorite grade and fluorite metallurgical recovery, the effect of each collector was determined, both in mechanical and pneumatic cell flotation. The effect of temperature on the collectors from 25 to 55 °C was studied. Flotation tests showed that the best results in terms of fluorite metallurgical recovery were 82.8% and 87.9% for new collectors DP-I and DP-II respectively, for a dosage of 100 g/t and using pneumatic cell. Additionally, in terms of fluorite grade, DP-I showed the best results, achieving 79.7% of CaF2 in roughing step for a dosage of 100 g/t. Fluorite metallurgical recovery and grade in concentrate increased for OA, SO and PO with increasing temperature. However temperature did not have a significant effect on both metallurgy recovery and CaF2 grade using DP-I and DP-II, so the process can be effective at 25 °C reducing operating costs.
J.R. Corpas-Martínez; A. Pérez; R. Navarro-Domínguez; C. Amor-Castillo; M.A. Martín-Lara; M. Calero. Testing of New Collectors for Concentration of Fluorite by Flotation in Pneumatic (Modified Hallimond Tube) and Mechanical Cells. Minerals 2020, 10, 482 .
AMA StyleJ.R. Corpas-Martínez, A. Pérez, R. Navarro-Domínguez, C. Amor-Castillo, M.A. Martín-Lara, M. Calero. Testing of New Collectors for Concentration of Fluorite by Flotation in Pneumatic (Modified Hallimond Tube) and Mechanical Cells. Minerals. 2020; 10 (5):482.
Chicago/Turabian StyleJ.R. Corpas-Martínez; A. Pérez; R. Navarro-Domínguez; C. Amor-Castillo; M.A. Martín-Lara; M. Calero. 2020. "Testing of New Collectors for Concentration of Fluorite by Flotation in Pneumatic (Modified Hallimond Tube) and Mechanical Cells." Minerals 10, no. 5: 482.
Serpentinites are characterized by highly variable mineralogical, physical, and mechanical properties. Serpentinites from Moeche (North Western Spain) have been studied to establish their mineralogical, petrographic, and textural characteristics, as well as their physical and mechanical parameters and the factors influencing rock failure, to evaluate the possible use of these rocks either for new construction or for conservation-restoration of the architectonic heritage of the region. In this paper, we highlight the importance of a detailed mineralogical and petrographic characterization in the fracture zones, which will determine the viability of quarrying the stone. A strong correlation between the petrographic features and the uniaxial compression strength values has been observed. The most important aspects were found to be the rock texture, the mineralogical composition of the fracture area and foliation, although mineralogy was also found to be involved (% of carbonates) in the strength of the stone. An important preliminary result of the study was the low asbestos content of these serpentinites, which will help in the potential re-opening of the quarries.
José Nespereira; Rafael Navarro; Serafín Monterrubio; Mariano Yenes; Dolores Pereira. Serpentinite from Moeche (Galicia, North Western Spain). A Stone Used for Centuries in the Construction of the Architectural Heritage of the Region. Sustainability 2019, 11, 2700 .
AMA StyleJosé Nespereira, Rafael Navarro, Serafín Monterrubio, Mariano Yenes, Dolores Pereira. Serpentinite from Moeche (Galicia, North Western Spain). A Stone Used for Centuries in the Construction of the Architectural Heritage of the Region. Sustainability. 2019; 11 (9):2700.
Chicago/Turabian StyleJosé Nespereira; Rafael Navarro; Serafín Monterrubio; Mariano Yenes; Dolores Pereira. 2019. "Serpentinite from Moeche (Galicia, North Western Spain). A Stone Used for Centuries in the Construction of the Architectural Heritage of the Region." Sustainability 11, no. 9: 2700.
Alternative processes have been proposed for selective separation of fluorite and gangue minerals (carbonates and silicates) present in fluorspar ores. Calcination and gravity separation processes are methods that have low efficiency and high cost. Flotation is a chemical process that becomes important when high ore grades are required; however, the selectivity is inhibited by the superficial similarity of the chemical composition of minerals. Accordingly, interactions between dissolved ionic species of fluorite, carbonates, and silicates with some reagents under determinate conditions obstruct the flotation process. In order to optimize the flotation process of a Spanish fluorite ore, this research uses a mathematical model. In this study, the variables were the dose of potato starch, quebracho tree, white dextrine, oleic acid, and sodium silicate. On the other hand, the factors studied were the law of carbonates, silica, and fluorite, in addition to the metallurgical recovery of fluorite. The statistical technique of factor analysis that relates the variables and factors allowed to the optimization of the reagent dosage. Maximum metallurgical recovery was achieved without sacrificing the fluorite grade. The mathematical model adjusts satisfactorily to the results with a correlation coefficient of 91.58% for metallurgical recovery and 98.51% for fluorite grade. Optimizing the process 60.45% of metallurgical recovery and 68.99% of fluorite grade are achieve in the roughing step, using a dosage of 1.68 g·kg−1 of potato starch, 0.86 g·kg−1 of quebracho tree, 1.25 g·kg−1 of dextrin, 3 g·kg−1 of oleic acid, and 0.85 g·kg−1 of water glass.
J.R. Corpas-Martínez; A. Pérez; C. Amor-Castillo; R. Navarro-Domínguez; M.A. Martín-Lara; M. Calero. Optimal Depressants and Collector Dosage in Fluorite Flotation Process Based on DoE Methodology. Applied Sciences 2019, 9, 366 .
AMA StyleJ.R. Corpas-Martínez, A. Pérez, C. Amor-Castillo, R. Navarro-Domínguez, M.A. Martín-Lara, M. Calero. Optimal Depressants and Collector Dosage in Fluorite Flotation Process Based on DoE Methodology. Applied Sciences. 2019; 9 (3):366.
Chicago/Turabian StyleJ.R. Corpas-Martínez; A. Pérez; C. Amor-Castillo; R. Navarro-Domínguez; M.A. Martín-Lara; M. Calero. 2019. "Optimal Depressants and Collector Dosage in Fluorite Flotation Process Based on DoE Methodology." Applied Sciences 9, no. 3: 366.
Colour is an important parameter that must be taken into account if aesthetic homogeneity in both construction and restoration work is to be achieved. In serpentinites, the different degrees of serpentinization or carbonation can influence their final colour. Sunlight, especially ultraviolet (UV) radiation, is a common agent that can decay properties such as hue, lightness, and chroma, and can have a very significant effect on the ageing process of dimension stones. Testing the effects of UV radiation is fundamental for predicting how materials may behave upon exposure. In this work, the surface alteration of materials due to UV radiation by means of arc-xenon lamps was carried out to determine the degree of variation in colour parameters in serpentinites used as dimension stones. It was observed that the effect of UV radiation on the materials studied was low, and that the samples tended to darken and become yellow. Gloss was the parameter that varied the most, which decreased in all the cases analysed. Associations were observed between the loss of gloss and a decrease in some parameters such as open porosity, water absorption at atmospheric pressure and water absorption by capillarity (direct), bulk density and uniaxial compression strength (reverse). The mineralogical composition of the stone was the main factor that influenced the loss of gloss. This research highlights the importance of the detailed study of colour variation in dimension stones due to exposure to UV radiation. The incorrect assessment of the damage that could be caused by this agent can lead to severe aesthetic destruction that may result in expensive legal actions.
Rafael Navarro; Lidia Catarino; Dolores Pereira; Francisco Gil. Effect of UV radiation on chromatic parameters in serpentinites used as dimension stones. Bulletin of Engineering Geology and the Environment 2019, 78, 5345 -5355.
AMA StyleRafael Navarro, Lidia Catarino, Dolores Pereira, Francisco Gil. Effect of UV radiation on chromatic parameters in serpentinites used as dimension stones. Bulletin of Engineering Geology and the Environment. 2019; 78 (7):5345-5355.
Chicago/Turabian StyleRafael Navarro; Lidia Catarino; Dolores Pereira; Francisco Gil. 2019. "Effect of UV radiation on chromatic parameters in serpentinites used as dimension stones." Bulletin of Engineering Geology and the Environment 78, no. 7: 5345-5355.
The ornamental use of marble from Macael region (Almería, southeast of Spain) began more than 5000 years ago. The first small objects are from the Neolithic period (3400–3000 B.C.) and the first known sculptures are from the Phoenicians period (fifth century B.C.) Since then, the marble’s use has been continuous, especially since the eleventh century. Some of the best known examples of Macael marble in Spain can be observed in Roman cities (e.g., Itálica), in Muslim buildings (e.g., Mosque of Córdoba or the Alhambra palace), or in Renaissance buildings such as the monastery of El Escorial, among many others. Some are declared World Heritage Sites by UNESCO. This makes the region one of the most important extraction centers in Spain, both at present and historically. The oldest and most famous variety of marble is known as White Macael (Blanco Macael). There are other marbles such as Gray Macael, Anasol Yellow Macael, and serpentinites which are traded as Green Macael. These have less importance in terms of their use in heritage but great importance in current regional trade. In this work, we provide a full characterization of the main characteristics of the White Macael marble from Macael and propose it as a candidate for “Global Heritage Stone Resource.” This work is important for duly recognizing a natural stone that has been used profusely in heritage buildings in the past and present with important international significance.
R. Navarro; D. Pereira; A. S. Cruz; G. Carrillo. The Significance of “White Macael” Marble Since Ancient Times: Characteristics of a Candidate as Global Heritage Stone Resource. Geoheritage 2017, 11, 113 -123.
AMA StyleR. Navarro, D. Pereira, A. S. Cruz, G. Carrillo. The Significance of “White Macael” Marble Since Ancient Times: Characteristics of a Candidate as Global Heritage Stone Resource. Geoheritage. 2017; 11 (1):113-123.
Chicago/Turabian StyleR. Navarro; D. Pereira; A. S. Cruz; G. Carrillo. 2017. "The Significance of “White Macael” Marble Since Ancient Times: Characteristics of a Candidate as Global Heritage Stone Resource." Geoheritage 11, no. 1: 113-123.
The heritage diversity that exists in the city of Granada in the south of Spain can be seen in the type of rock from which the majority of the emblematic monuments are built, especially since the 15th century. There are three main lithotypes extracted in the province of Granada which are present in most of the heritage buildings in the city centre. These rocks are known as “Santa Pudia” calcarenite (Tortonian), “Sierra Elvira” limestone (Lias) and “Alfacar” travertine (Quaternary). It gives an outstanding aesthetic and ornamental richness to the city. Besides these, there are other lithologies from the province, such as conglomerate from El Turro, marble from Lanjarón, limestone from Loja and serpentinite from Sierra Nevada, which have also been used occasionally. In this paper we show a detailed characterization of these materials, including quarry provenance, main mineralogical and physical characteristics, main uses in different buildings and major deterioration problems that these stones may have. An adequate knowledge of the materials with which the different architectural elements of the city were built, contribute to executing appropriate restoration and contribute to the proper maintenance of the heritage of the city. With this contribution we suggest that the province of Granada should be considered as a “Global Heritage Stone Province”, given that the richness and variety of natural stone used in its monuments is more than proven.
Rafael Navarro; Josefina Sánchez-Valverde; José Manuel Baltuille. The Natural Stone in the Historic Buildings of the City of Granada (Southern Spain). Features as a Possible Candidate for the Designation of “Global Heritage Stone Province”. Engineering Geology for Society and Territory - Volume 5 2014, 229 -232.
AMA StyleRafael Navarro, Josefina Sánchez-Valverde, José Manuel Baltuille. The Natural Stone in the Historic Buildings of the City of Granada (Southern Spain). Features as a Possible Candidate for the Designation of “Global Heritage Stone Province”. Engineering Geology for Society and Territory - Volume 5. 2014; ():229-232.
Chicago/Turabian StyleRafael Navarro; Josefina Sánchez-Valverde; José Manuel Baltuille. 2014. "The Natural Stone in the Historic Buildings of the City of Granada (Southern Spain). Features as a Possible Candidate for the Designation of “Global Heritage Stone Province”." Engineering Geology for Society and Territory - Volume 5 , no. : 229-232.
Verde Macael is a serpentinite made up mainly by antigorite, with different degrees of transformation to carbonates. It has wrongly been included under the section of marbles in industry catalogues. In Macael (Almería, South Spain) there are different quarries extracting this natural stone. Although in most outcrops rocks are similar, different characteristics are detected derived from transformation processes. The results are shown in variations in mineralogy, texture and/or in the physical and mechanical properties, conditioning the behaviour of the natural stone once emplaced in a building. The main factor of variation is related to the carbonation degree. Due to its late use in some significant heritage buildings such as the cathedral of Nuestra Señora de La Almudena in Madrid or many civil buildings all over the country, a whole characterization of the material from the main quarries is an important task we face in this work. We test the main parameters that determine its proper use in civil construction. This will help to avoid early deterioration of the natural stone and subsequent costs for restoration. Due to the characteristics of Verde Macael this rock is a possible candidate to Global Heritage Stone resource designation.
Rafael Navarro; Dolores Pereira; Ana Gimeno; Santiago del Barrio. Characterization of the Natural Variability of Macael Serpentinite (Verde Macael) (Almería, South of Spain) for Their Appropriate Use in the Building Industry. Engineering Geology for Society and Territory - Volume 5 2014, 209 -212.
AMA StyleRafael Navarro, Dolores Pereira, Ana Gimeno, Santiago del Barrio. Characterization of the Natural Variability of Macael Serpentinite (Verde Macael) (Almería, South of Spain) for Their Appropriate Use in the Building Industry. Engineering Geology for Society and Territory - Volume 5. 2014; ():209-212.
Chicago/Turabian StyleRafael Navarro; Dolores Pereira; Ana Gimeno; Santiago del Barrio. 2014. "Characterization of the Natural Variability of Macael Serpentinite (Verde Macael) (Almería, South of Spain) for Their Appropriate Use in the Building Industry." Engineering Geology for Society and Territory - Volume 5 , no. : 209-212.
Serpentinites are used in both exterior and interior locations, but not all serpentinites are equal: they vary in physical-mechanical behavior and are not all suitable for similar uses. The serpentinites most commonly used worldwide come from India, Pakistan or Egypt. Spain has traditionally quarried two ultramafic massifs, one in Galicia (Verde Pirineos) and one in Andalucía (Verde Macael). Some of these quarries were small family-run businesses. In both cases, these rocks are commercially available as “green marble.” These serpentinites commonly have a high degree of carbonation, but the process does not always take place with the same intensity. Carbonate can act as a cementing agent of the other phases, increasing the mechanical strength parameters. As a result, an improvement in the strength conditions is achieved, but a misinterpretation of the suitability of the rock may occur because a perception among users that “green marble” is similar to geologically defined marble. This may lead to inappropriate applications as an ornamental stone. At a time of economic crisis in Europe, the natural stone sector is encouraged to invest in research to identify the best quality products that can compete profitably with those currently being imported from other countries. This paper provides a comparison of properties of the Verde Macael serpentinite with a true marble in the hope of contributing to improving the natural stone industrial sector
Rafael Navarro; Dolores Pereira; Ana Gimeno; Santiago Barrio. Verde Macael: A Serpentinite Wrongly Referred to as a Marble. Geosciences 2013, 3, 102 -113.
AMA StyleRafael Navarro, Dolores Pereira, Ana Gimeno, Santiago Barrio. Verde Macael: A Serpentinite Wrongly Referred to as a Marble. Geosciences. 2013; 3 (1):102-113.
Chicago/Turabian StyleRafael Navarro; Dolores Pereira; Ana Gimeno; Santiago Barrio. 2013. "Verde Macael: A Serpentinite Wrongly Referred to as a Marble." Geosciences 3, no. 1: 102-113.