Ornamental Stone Research Articles

Microcracking based rock classification using ultrasonic and porosity parameters and multivariate analysis methods

This work aims at presenting a new methodology, based on NDT ultrasonic techniques and water porosity measurements, to characterize the microcracking state of rocks and classify them in microcracking based equivalent groups. The measurements of ultrasonic pulse velocity, the attenuation coefficient and the porosity by water saturation under vacuum conditions make it possible to compare and validate all these techniques as good practices to classify aggregates and ornamental stones with regard to their rock matrix compactness.Beyond the fact that these developments give new approaches to assess the rock microcracking, it was shown that these parameters have a direct relationship. Indeed, the classification methodology was applied to a database containing 56 cores coming from blocks sampled in an aggregate production quarry. For these cores, ultrasonic parameters (wave velocity, attenuation and anisotropy coefficients) and porosity parameters (total water, crack and pore porosities) were measured. Two multivariate statistical methods (Principal Component Analysis and Cluster Analysis) were applied on this database to assess the relationship between all these parameters and to classify the cores into micro-structurally similar groups.The application of the setup methodology on the core database allows us to study the main correlations between the measured microcracking rock properties. On the other hand, it was shown that the method can be used as an effective way to characterize the differences in terms of microstructure between rock samples.

A multi-technique approach for the characterization of decorative stones and non-destructive method for the discrimination of similar rocks

In this paper, a multi-technique approach, at different scale of observation, is used to characterize a group of decorative stones and to permit to distinguish rocks with similar aspect but coming from different areas. In particular, the samples under study are sedimentary and metamorphic rocks, widely used as building blocks of modern and historical constructions and sculptures. The petrographic and mineralogical features of such rocks were performed by optical microscopy and Raman and Fourier transform infrared absorbance spectroscopies. These techniques permitted to obtain a complete structural, textural, and mineralogical characterization. At elemental level, the investigation was carried out by X-ray fluorescence (XRF). In particular, XRF and Raman measurements were collected using portable instrumentations, whose advantages for the in situ analysis have been pointed out. The obtained results evidenced the high discriminant capability of the portable XRF for the decorative stones especially when this method is coupled with mineralogical and petrographic information. In this context, we propose to create a database for precious ornamental stones, which could be a starting point for a non-destructive characterization, even useful for provenance study and/or certification of origin. Copyright © 2013 John Wiley & Sons, Ltd.

Durability performance of concrete incorporating coarse aggregates from marble industry waste

Abstract The quarrying of marble, a well-known ornamental stone, has a substantial positive impact on Portugal's economy, but it also generates large environmental impacts. The amount of waste produced during quarrying can be as much as 80% of all stone/soil extracted. That waste is then dumped near the quarry, where it accumulates indiscriminately because a viable alternative for its disposal has not yet been found. In this context, solutions must be found that can transform this waste into a by-product and restore some of its economic value. The main goal of this study was to evaluate the influence of the replacement of primary aggregates (PA) with marble aggregates. No additions or admixtures were used, as those could change the fresh or hardened properties of the resulting concrete and disguise the influence of the replacement under study. This evaluation required the production of three concrete families. The conventional primary aggregates (PA; basalt, granite and limestone) were replaced in the three families by coarse marble aggregates (CMA) at ratios of 20%, 50% and 100% of the total volume of aggregates. These mixes were tested in the concrete's fresh state for workability and density and in its hardened state for compressive strength, water absorption by capillarity and immersion, carbonation and chloride penetration. The results indicate that there are no significant differences between a concrete produced using CMA and one made with PA in terms of durability, making the use of this waste as concrete aggregate perfectly feasible. The mechanical properties of the concrete made with CMA were assessed in the scope of concurrent work also performed at the Instituto Superior Tecnico (Lisbon, Portugal).

Characterization of the lapis lazuli from the Egyptian treasure of Tôd and its alteration using external μ-PIXE and μ-IBIL

Lapis lazuli is among the earliest and most priced ornamental stone worked to produce carvings, beads and inlays as early as the 4th millennium BC. It is an heterogeneous rock composed of blue lazurite Na3Ca(Si3Al3O12)S mixed with other minerals like calcite, diopside and pyrite. The historical source of lapis lazuli in antiquity is supposedly located in Afghanistan, in the Sar-e-Sang district, while other sources are known in Tajikistan and Russia (Baïkal area).This work focuses on the lapis-lazuli of the Egyptian treasure of Tôd dated from Middle Kingdom (20th c. BC). Deposited in four copper boxes, it consists of thousands of blocks of raw lapis lazuli, minute fragments, beads and carvings stylistically dated to various periods. This discovery raises the question of the use of lapis lazuli in ancient Egypt because there is no source of lapis in this country. In addition, most of the lapis lazuli artefacts are strongly weathered. The aim of this work is to understand the alteration process and to verify if its provenance can still be determined.A few artefacts were analysed using the new external microbeam line of the AGLAE facility of the C2RMF. The mineral phases were identified and corresponding trace elements (e.g. Ti, As, Ni, Ba) were ascribed using the quantitative PIXE elemental maps collected on the entire artefacts or on cross-sections. In parallel, the IBIL spectrum recorded for each point in the image provided an additional fingerprint of the luminescent phases, notably mineral species belonging to the cancrinite group. Most alteration products appeared to derive from the oxidation of the pyrite FeS2. It was observed that the alteration process extends to the core of most investigated artefacts. Despite such a strong alteration state, the chemical fingerprints recorded on the studied artefacts proved to be consistent with that of lapis lazuli from historical deposit of Badakshan, Afghanistan, previously investigated using the same μ-PIXE/μ-IBIL protocol.

English

  The present study has dealt with the field and microscopic description of different building, industrial and ornamental stones of the Tertiary sedimentary succession of Haddat Ash Sham area, Saudi Arabia. The described building and ornamental stones includes: quartz pebble conglomerates, sandstones, limestones, dolostones and clays. The stratigraphic setting, mega and microscopic description of the different types of building and ornamental stones revealed the predominance of the quartz-pebble conglomerates in the lower and upper members of the Tertiary succession of the study area while the clays and carbonates are present in the middle member of this succession. The quartz pebble conglomerates represents the most important building material which is mostly suitable for concrete industry while the sandstones are present as very thick hard ferruginous cliffs suitable for dimensional blocks for facing and decoration. The carbonates are represented by relatively thin horizons of limestone and dolostones which is easily extracted and used for concrete industry. The clay deposits are present in many levels within the sedimentary succession of Haddat Ash Sham area and represent the same extensions of the clay quarries used for brick industry in Ash Shamiyah area west of Haddat Ash Sham area. The studied building and ornamental stones need further engineering tests and measurements for the accurate evaluations from the engineering points of views. The reserves of the clay deposits must be evaluated from the economic points of views for cement and ceramic industries.   Key words: Saudi Arabia, Haddat Ash Sham area, building and ornamental stones, quartz pebble conglomerates and concrete materials.

Study of a tabernacle with a remarkable architectural structure: In situ examination using Raman spectroscopy

In order to characterize ornamental stones and gemstones from the monstrance ‘Tabernáculo de la Colegiata de S. Pedro’ in Lerma, Burgos, a Raman spectroscopy in situ non‐destructive study has been performed on these materials.The Raman spectra obtained correspond to cornalline‐like chalcedony, nephrite jade, quartz veinlets, agates with moganite and jasper, together with goethite showing several degrees of alteration. Various types of marble and lapis lazuli were identified.The lapis lazuli samples show different Raman spectra depending on the blue–white chromatic gradient, due to the variations in the sulfur concentration. Raman spectroscopy allows for the correlation of the presence of radical molecular ions S2−, S3− and SO42−, with the colour centres and colouration of lapis lazuli.Two varieties of marble are present, one of brown tones with greyish‐white incrustations and another with alternating white and black veinlets with yellow inclusions. In the former, white masses of microcrystalline calcite appear together with quartz inclusions, around which brown halos of goethite develop as an alteration product. In the latter, they show calcite in the white veinlets and calcite with graphite in the black ones. The mineralogical analysis of ornamentals stones on art objects allows determining their degree of conservation and the extension of the deterioration, in order to establish strategies for the cleaning and restoration. These results are an important factor to date the object and for shedding light about its authorship. Furthermore, it could eventually help to establish connections between the tabernacle‐monstrance and other tabernacles in Castilla y León. Copyright © 2013 John Wiley & Sons, Ltd.

Aspectos de vida, trabalho e saúde de trabalhadores do setor de rochas ornamentais

The process of health and disease is socially determined, whereby work is a factor that strongly influences the morbidity/mortality profile. The scope of this article is to study the relationship between work and health conditions reported by the workers of the ornamental stone industry and residents from the district of Cachoeiro de Itapemirim, State of Espírito Santo. It is an epidemiological cross-sectional study with data collection through a questionnaire applied to 187 workers at their homes using statistical, descriptive and analytical methods. A considerable percentage of workers stated self-reported acute morbidity (45.5%) and chronic morbidity (44.9%), as being related to work (56.5% and 51.2% respectively). Despite the broad perception by the workers of the risks of the environmentally insalubrious work conditions, those who cited morbidity related the ergonomic aspects of work to musculoskeletal disorders in the main group of disorders presented. The high percentage of morbidity is the result of these individuals being subject to a work-related process where the conditions and the work organization cause physical and mental strain, being determined by the way work is socially divided in that sector.

New contributions to granite characterization by ultrasonic testing

Ultrasound evaluation permits the state of rocks to be determined quickly and cheaply, satisfying the demands faced by today’s producers of ornamental stone, such as environmental sustainability, durability and safety of use. The basic objective of the present work is to analyse and develop the usefulness of ultrasound testing in estimating the physico-mechanical properties of granite. Various parameters related to Fast Fourier Transform (FFTs) and attenuation have been extracted from some of the studies conducted (parameters which have not previously been considered in work on this topic, unlike the ultrasonic pulse velocity). The experimental study was carried out on cubic specimens of 30cm edges using longitudinal and shear wave transducers and equipment which extended the normally used natural resonance frequency range up to 500kHz. Additionally, a validation study of the laboratory data has been conducted and some methodological improvements have been implemented.The main contribution of the work is the analysis of linear statistical correlations between the aforementioned new ultrasound parameters and physico-mechanical properties of the granites that had not previously been studied, i.e., resistance to salt crystallization and breaking load for anchors. Being properties that directly affect the durability and safety of use of granites, these correlations consolidate ultrasonics as a nondestructive method well suited to this type of material.

Pseudomonas,PantoeaandCupriavidusisolates induce calcium carbonate precipitation for biorestoration of ornamental stone

Bacterially induced calcium carbonate precipitation from various isolates was investigated aiming at developing an environmentally friendly technique for ornamental stone protection and restoration. Micro-organisms isolated from stone samples and identified using 16S rDNA and biochemical tests promoted calcium carbonate precipitation in solid and novel liquid growth media. Biomineral morphology was studied on marble samples with scanning electron microscopy. Most isolates demonstrated specimen weight increase, covering partially or even completely the marble surfaces mainly with vaterite. The conditions under which vaterite precipitated and its stability throughout the experimental runs are presented. A growth medium that facilitated bacterial growth of different species and promoted biomineralization was formulated. Most isolates induced biomineralization of CaCO3 . Micro-organisms may actually be a milestone in the investigation of vaterite formation facilitating our understanding of geomicrobiological interactions. Pseudomonas, Pantoea and Cupriavidus strains could be candidates for bioconsolidation of ornamental stone protection. Characterization of biomineralization capacity of different bacterial species improves understanding of the bacterially induced mineralization processes and enriches the list of candidates for biorestoration applications. Knowledge of biomineral morphology assists in differentiating mineral from biologically induced precipitates.

Diamond recovery from waste sawblades: A preliminary investigation

Due to their excellent hardness and toughness, diamond tools have been widely used as cutting tools for mining applications such as machining and/or processing of natural stones. A considerable amount of used sawblades with diamond grits are damaged, scrapped and wasted in the regions where machining and/or processing of ornamental stones are heavily conducted. Since a damaged and/or scrapped sawblade could still have diamonds grits, the recovery of diamond grits from sawblades has recently gained attention. The aim of this study was to investigate the recoverability of diamonds from damaged sawblades using hydrometallurgical processes, including aqua regia. Using scanning electron microscopy micrographs, the worn surfaces of diamonds were also examined before and after leaching. The results of the study represented that the diamonds from damaged sawblades can be successfully recovered by hydrometallurgical processes, including aqua regia, and the recovered diamonds could be reused in cutting tools after size classification. The results also revealed that among the damage types of diamond, the fractured and polished crystals resulted in diamond crystals with lower grain size.

Rock Finishing and Response to Salt Fog Atmosphere

Seven silicate rocks used as ornamental stones and having different surface finishing were submitted to salt fog atmospheres in order to compare different susceptibilities to alteration. Polished, honed, hammered and flamed finishing types were tested. Rocks come from Portugal, Brazil and Angola and are widely commercialized. Samples covered quartz rich rocks, silica saturated and undersaturated rocks, mono and plurimineralic rocks, coarse and fine grained rocks. Mineral composition, texture and open porosity showed to be important parameters which determine mass loss among samples, but the finishing type was very effective within samples. Mass loss and porosity increase are higher on hammered samples, contrasted with the lowest loss values on polished samples. The effect of surface hydrophobicity and roughness on the samples having polished finishing was also analysed by atomic force microscopy (AFM) and water contact angle (WCA), indicating that texture and mineral diversity influence the hydrophobic character of the rock surfaces.

The “Alpalhão Granite” (Alentejo, Portugal) as a Potential Ornamental Stone

“Alpalhão granite”, also called SPI, is used as a high quality ornamental stone for interior and exterior applications. It is fine grained and equigranular, and has disseminated feldspar phenocrysts showing a homogeneous bluish grey colour. The SPI was mapped and scanlines (14) and drill cores (4) were carried out for lithofacies and joints characterization, besides petrographical study. Three of the 5 granite outcrops were studied regarding their potential for ornamental blocks exploitation (Carvalhal, Pinheiral and Ribeira de Sor). The Carvalhal area has generally no potential, due to intense fracturing and frequent heterogeneities except for drill core SCA1 area. The Pinheiral area has been exploited in all its extent, but still assures 368,800m3 estimated resources of good granite at depth. Ribeira de Sor area presents a good potentiality for commercial blocks in the eastern zone and a limited potential in the western area due to subsurface fracturing and chromatic changes.

Evaluation of the Portuguese Ornamental Stone Resources

Portugal produces a great diversity of ornamental stones. Besides the internationally known white and pink marbles, also light cream limestones are produced, as well as grey, yellow and pink granites, and dark grey slates. A first exercise is presented on the evaluation of the available resources of ornamental stones in the whole Portuguese territory. The results show a total availability of 410 million cubic meters, of which 274 million refer to granite, 76 million to limestone, 51 million to marble, and 9 million to slate.

Finite Element Model Development Applied to Portuguese Granites for Contact Analysis of Two Dowel Fixing Conditions Used in Cladding

The present work sets out a finite element model for contact analysis of two different dowel fixing conditions for granite cladding. To be used in building facades as cladding materials and ornamental stones, Portuguese granites Cinzento de Alpalhão (SPI) and Amarelo de Vila Real (AVR) are considered with dowel-hole anchorage systems. FEM for contact analysis was developed (with ANSYS software) for two different dowel fixing conditions: one with regular plastic cap and the other with a fast curing mortar. Differences on strain fields between both granites with the different dowel fixing conditions were studied. Contact analysis for SPI and AVR materials show that the different dowel fixing conditions originate different strain fields. FEM results explain how different contact conditions influence the overall system stiffness (stone panel – fixing element – dowel) obtained in the dowel-hole anchorage strength tests for both granites.

Application in Pottery of the Residual Soils Associated to Marbles from the Estremoz Anticlinal Region

Terra rossa is a residual soil that is derived from the chemical dissolution of carbonate rocks. This type of soil occurs in the region of the so-called Estremoz anticlinal, being the result of the weathering of extensive marble occurrences which are exploited for ornamental stone. The research work performed and disclosed in the present paper shows that terra rossa possesses appropriate compositional and technological properties for its use on ceramic applications, particularly for the local traditional pottery. In potential marble quarry sites several thick soil horizons can be found, and whenever the soil is removed marble is shown up. As a rule, the removed soil is deposited around the quarry, and so far no use has been given to it. Pottery has a long tradition in the Alentejo region, and Vila de Redondo and Aldeia de S. Pedro do Corval are known as emblematic centers of this activity. However, time has shown that the scarcity of high quality clay deposits has become an important issue. Therefore, potters are buying clay from other regions of Portugal, in particular in the area of Caldas da Rainha, located in the central west of the country and far from Alentejo, or even importing it from Spain. The cooperative research work carried out in the Laboratories of DGUE, the Department of Geosciences at the University of Aveiro (DGUA) and CENCAL, and at the pottery owned by the artisan Mestre Xico Tarefa, in Vila de Redondo, has shown that terra rossa, due to its physicochemical, mineralogical and technological properties, can be used as a raw material in ceramic manufacturing, particularly in the traditional pottery produced both in Redondo and S. Pedro de Corval.

Use of Waste from Ornamental Stones Processing in Landscaping Blocks

The State of Espírito Santo (Southeastern Region of Brazil) produces about 80% of Brazilian exports of natural Stones, which are mainly directed to European countries and the USA. The city of Cachoeiro de Itapemirim and the surroundings account for about 90% of the State’s production. The mineral sector is the main economic activity in the area and responsible for the generation of thousands of direct and indirect jobs. Before the finished products reach the market, blocks, extracted from the quarries, go through several processes as splitting, cutting and polishing. Each one of those stages generates a substantial quantity of waste in the form of mud. Estimation for Cachoeiro de Itapemirim is around 60,000 tons/month of that kind of waste. The main objective of this work was the construction of low cost landscaping blocks, using residues of marbles and granites processing, from companies located in Cachoeiro de Itapemirim. It also aims to test their use in degraded areas, with a high degree of slope that are resulting from erosion and human activity, thus stabilizing the slope and minimizing future landslides. Waste was used in the form of mud, with fine particle size, mixed with cement and sand, in varying proportions to produce landscaping blocks. Physical indexes, visual inspection, dimensional verification, compression strength, flexural strength, and mineralogical and chemical analyses were obtained for the blocks. The results are positive regarding mechanical resistance.

Relationship between Breaking Moments at the Dowel Hole and at Flexure under Concentrated Load of Ornamental Stones

During its more than ten-year active life, numerous tests have been performed at LITHOS Laboratory for determining various physical mechanical properties on a significant variety of ornamental stones from Greece and abroad, in compliance with the applicable EN Standards. Given the somewhat evident similarity observed for the breaking mechanism on specimens during determination of the breaking load at dowel hole (EN 13364) and that of flexural strength under concentrated load (EN 12372), an attempt has been made to correlate the relevant results. The objective was to investigate the possibility of creating a potential practical tool for a first estimation of the breaking load at dowel hole, having performed only the much simpler flexural strength determination test. After the appropriate statics approach that has been developed for each test to simulate the relative breaking mechanisms followed by the specimens and the analysis of all the data available, it has been revealed that a linear relationship combining the breaking moments exerted on the specimens in both the aforementioned tests may be established. Taking into account the wide range and diversity of the types of ornamental stones employed, the correlation coefficient calculated for the linear equation describing this relationship is considered sufficient for serving the objective set for this experimental research work.

Verde Macael: A Serpentinite Wrongly Referred to as a Marble

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.

In situ stress measurements interpretations in large underground marble quarry by 3D modeling

This paper describes the studies and the in situ stress measurements carried out to support the stability analysis of underground ornamental stones quarries. In particular, this paper describes the findings, evidence and analysis carried out at the Ravaccione and Fantiscritti quarries, which are located in the Carrara basin, Italy. The main activities carried out during the study are starting with the characterization of the rock mass which has been done through the interpretation of data obtained from in situ geostructural surveys, combining the geometrical and mechanical characteristics of the discontinuities with the mechanical features of the rock matrix in order to assess the proper rock index in accordance with the more diffused classification systems. Further consideration regarding the tectonic stress orientation are done through the observation of kinematic indicators on brittle structures-such as faults, fractures s.l. (joints s.s., and fractures with no evidence of movement) and systems of conjugated fractures, in order to evaluate the tectonic stress main orientation for the studied area. Then several in situ measurements of actual state of stress on various location inside the Ravaccione and Fantiscritti quarries where carried out using CSIRO cells. This preliminary work lead to the geometric reconstruction of the rock mass, carried out using the computer code Resoblock®. This phase allowed, once the current excavation geometry was given, to define the geometry of a discontinuous rock mass model on which, thereafter, a numerical simulations was carried out using the computer code 3DEC®. At last, the comparison between the numerical model results and the in situ tests allowed the back analysis of the site and lead to a most satisfying model calibration to be used for the provisional analysis of further excavation development.

The Development of Decision-Making Maps for the High-Speed Machining (HSM) of Rhyodacite (Carijó Basalt) in Milling-Based Processing Applications

The demand for innovative products that overcome competitive pricing and conquer market shares can be met by interdisciplinary approaches that bridge product design, engineering and technology. Ornamental and covering stones stand out among the materials in need of innovation and are commonly used in architecture and construction as coverings in urban elements, funerary art, and art and decor. In spite of the many applications of ornamental stones, products with low added value are typically observed. Although Brazil displays significant geological potential for ornamental stones, its actual market participation is as a supplier of un- or semi-processed stones. Even with the market’s visible expansion and Brazil’s increased representation in the market, the technological advances used in the final processing of stones are restricted to improve the tools used for cutting, especially the durability of diamond-coated tools, and for polishing, which, in the short-term, meets the demands for marketing, producing and distributing semi-finished products. Accordingly, a little exploited aspect of ornamental stones appears, especially for “carijo basalt” (rhyodacite), that is, the inclusion of new processing and value-adding technologies or the inclusion of non-conventional processes in the sector. The goals of this work are to study and develop HSM (high speed machining) CNC (computer numerically controlled) milling processes that are applicable to rhyodacite, specifically to determine the milling parameters that give the best results for machining time with respect to tool wear and material abrasion and to replicate the results obtained in the samples. The results show that the raw material used in the present study, because it is natural, presents significant variations in composition and hardness, which prevent specific milling parameters from being determined. However, using a post-processor specifically developed for this study, it was possible to draft a decision-making map that aids in the execution of this process. Additionally, equipment failure occurred during every attempt and with every adjustment of the milling process. This indicates that the application of multipoint tools to rhyodacite milling is difficult in this industry. Thus, the use of single-point tools should be the natural path to follow for a potential practical industrial application in Brazil.