Marble Varieties Research Articles

A New Approach for Provenance Studies of Archaeological Finds: Inferences from Trace Elements in Carbonate Minerals of Alpine White Marbles by a Bench-to-Top μ-XRF Spectrometer

The metamorphic rocks outcropping in the Western Alps are characterised by a great variety of white marbles which have been used since the antiquity. This variety mostly includes nine historical Piedmont white marbles (Ornavasso, Candoglia, Crevola, Pont Canavese, Foresto, Chianocco, Prali, Brossasco, and Garessio marbles) coming from well-known quarry sites and belonging to different metamorphic geological units of the Western Alps. The petrographical, minerochemical, and C–O isotopic data of these white marbles have been integrated with CaO and trace element (Fe, Mn, and Sr) concentration determined on single crystals of carbonate minerals (i.e., calcite and/or dolomite) by means of a bench-to-top µ-XRF spectrometer. Principal component analysis and hierarchical cluster analysis were performed on a data set of 178 observations containing CaO, Fe, Mn, and Sr concentration as well as the maximum grain size (MGS), δ18O and δ13C. The use of only five selected variables (CaO, Fe, Mn, Sr, and δ18O) has provided the correct allocation of each individual observation to its relevant class. Therefore, this approach based mostly on a noninvasive µ-XRF determination will be useful to define the provenance of unknown marbles of alpine origin used in antiquity for cultural heritage.

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.

White and Coloured Marbles of the Roman Town of Urbs Salvia (Urbisaglia, Macerata, Marche, Italy)

SummaryThe results of an archaeometric study concerning the coloured stones and 14 white marble sculptures found in the ancient city of Urbs Salvia (Urbisaglia, Macerata) – one of the main Roman archaeological sites of the Marche region (east central Italy) – are presented here. Data show the presence of the most important decorative stones used by the Romans, originating in all of the Mediterranean provinces, from Egypt and North Africa to Asia Minor, Greece, Gallia, Iberia and Italy. Thirty‐one different coloured lithotypes have been identified, including red and green porphyries as well as marmor phrygium and numidicum, namely the four most expensive stones cited in Diocletian's edict. Crustae of marmor chium, taenarium, chalcidicum, scyreticum, lucullaeum and sagarium also feature. Another significant presence is that of coloured stones that are generally rare, even in Rome and Ostia, such as cipollino mandolato (which is very abundant at Urbs Salvia, more than anywhere outside Gallia), broccatello di Spagna, alabastro a pecorella, lapis ophytes, brecciated facies of marmor iassene and cottanello antico. Worthy of mention, too, is the abundant presence of so‐called Roman breccia from Lez (Upper Garonne valley, French Pyrenees), a stone never reported outside Gallia. The 14 marble sculptures analysed come from public and private buildings of the Roman city and are now exhibited at the Archaeological Museum of Urbisaglia. Our petrographic and isotopic analyses show that they are made of Lunense (five), Pentelic (three), Parian lychnites (three), Thasian (three) and Proconnesian (one Corinthian capital) marbles. The quality of the coloured stones identified, together with the presence of sculptures made of precious imported white marble varieties, reveals an opulent town and a local patronage wishing to decorate public buildings and rich houses with the most sought‐after marbles of Rome.

Effect of mineralogical and microstructural properties on surface roughness and gloss of some ornamental marbles subjected to polishing process

High surface finish quality of the produced slabs is generally desirable in the stone processing industry. This paper presents the results of an experimental investigation into the effects of mineralogical-petrographical and chemical variables on the surface roughness and glossiness of some selected ornamental marbles subjected to grinding–polishing processes. For this purpose, a series of grinding–polishing procedures were performed on the slabs of three distinct marble types. Roughness and brightness measurements were carried out on predetermined surfaces of marble samples using a stylus profilometer and a glossmeter, respectively. Thin sections were examined by a polarizing microscope for mineralogical-petrographical characterization of the studied marbles. Scanning electron microscopy was used to aid in the identification and characterization of the slab surface morphologies at each polishing stage. X-ray diffraction and scanning electron microscopy with energy-dispersive X-ray spectroscopy were used for the determination of mineralogical and chemical compositions of the samples. Mainly because of the differences in textural and chemical compositions, different levels of microroughness and gloss values were observed for the studied marble varieties. The presence of different mineral phases such as the grain (i.e. calcite to calcite) and phase contacts (i.e. calcite to epidote) greatly affected the heterogeneity of the marbles, resulting with different removal mechanisms under the action of abrasive grits. Copyright © 2013 John Wiley & Sons, Ltd.

Radiological significance of marble used for construction of dwellings in Bangladesh

The natural γ-radiation in samples of a variety of marbles imported into Bangladesh for use in building construction was measured, employing γ-ray spectrometry with a HPGe detector. From the measured γ-ray spectra, activity concentrations were determined for 226 Ra (29.31 ± 2.06 to 46.99 ± 2.97 Bq.kg–1 ), 232 Th (42.91 ± 2.53 to 62.92 ± 3.37 Bq.kg–1 ) and 40 K (824.42 ± 15.42 to 1071.58 ± 20.14 Bq.kg–1 ). The measured activity concentrations for these natural radionuclides were compared with the reported data of other countries and with the world average activity of soil. The radium equivalent activity (Raeq ), the hazard indices, the gamma activity concentration index, the indoor absorbed dose rate and the corresponding annual effective dose were estimated for the potential radiological hazard of the marble. The Raeq values of all marble samples are lower than the limit of 370 Bq.kg–1 , equivalent to a dose of 1.5 mSv.y–1 . The average values of the external and internal hazard indices are less than unity. The average indoor absorbed dose rate (121.25 nGy.h–1 ) is higher than the population-weighted average of 84 nGy.h–1 , whereas the corresponding annual dose limit falls within an average value of 0.60 mSv, which is an order of magnitude below the limit specified for building materials in the literature. The present results indicate that using marble in building construction in Bangladesh does not pose any significant radiological hazard.

ON THE WHITE AND COLOURED MARBLES OF THE ROMAN TOWN OF CUICUL (DJEMILA, ALGERIA)

This paper reports the results of an archaeometric study of the local and imported marbles found in the Roman town of Cuicul (now Djemila, Algeria), a research project funded by the Sixth Framework Programme of the European Union. Of the few imported coloured lithotypes that have been found, four are of Greek origin and one was imported from Asia Minor. In addition, two other classical Roman coloured stones found on the site are probably of local North African origin (most likely one from Numidia and one from Algeria). With regard to the grey and white marbles employed in the statuary and architecture, petrographic study in thin section and the δ13C and δ18O isotopic data emphasize the frequent use of the local fine‐grained lithotype from Filfila (Skikda) together with imported Greek lithotypes (i.e., Pentelic marble, the dolomitic variety of Thasian marble, and Parian marble from Lakkoi) as well as different varieties of the so‐called ‘greco scritto’, whose provenance in some cases still remains uncertain. In fact, the petrographic and geochemical features of the marbles do not always match those known for the classical ‘greco scritto’ from the quarry of Cap de Garde, near Annaba (Algeria).

Laser-induced breakdown spectroscopic studies of marbles

We present laser-induced breakdown spectroscopic studies of variety of marbles extracted from Quetta region of Boluchistan, Pakistan using a Nd:YAG laser (532 nm) in conjunction with LIBS 2000 detection system. The emission spectra of Onyx (white spot) and Quetta Green Marble samples have been recorded as a function of laser irradiance. The elemental composition and their relative abundance in each sample are fond to be quite different. In Onyx (white spot), calcium dominates while in the Quetta Green marble magnesium is the dominant element. In addition the effect of the laser irradiance on the emission intensity, width and shift of the transition lines have been studied.

THE PIEDMONT WHITE MARBLES USED IN ANTIQUITY: AN ARCHAEOMETRIC DISTINCTION INFERRED BY A MINERO‐PETROGRAPHIC AND C–O STABLE ISOTOPE STUDY*

The metamorphic rocks outcropping in the Western Alps are characterized by a great variety of white marbles, which have been poorly studied in the archaeometric field even though they have been used since antiquity. Typical examples are the Arc of August of Roman times in Susa (Piedmont, Italy) and lots of monuments and historical buildings of Turin (Italy). A multi‐analytical approach based on petrographic (optical and scanning electron microscopy), electron microprobe and stable isotope analysis of Piedmont white marbles has been performed in order to carry out a detailed description, summarizing their main microtextural, mineralogical and isotopic features. Eight historical Piedmont marbles have been sampled from well‐known quarry sites belonging to different metamorphic geological units of the Western Alps (Ornavasso, Crevola, Pont Canavese, Foresto, Chianocco, Prali, Brossasco and Garessio marbles). Their different metamorphic conditions, ages and structural evolution allowed us to draw a discriminative flowchart based on microscopic and minero‐chemical data.

Pretreatment of African Yam Bean (Sphenostylis stenocarpa): Effect of Soaking and Blanching on the Quality of African Yam Bean Seed

The effect of pretreatment (soaking in sodium salts and blanching) on hydration coefficient (HC), chemical composition, texture, and color of African yam bean (AYB) was investigated. Soaking in water and in salt solutions increased the HC and about 90% of final HC values were attained at 12 and 4 hr of soaking for whole and dehulled beans, respectively. Protein content was slightly increased by soaking and blanching while ash and fat contents were reduced. Generally, a combination of dehulling and wet-processing reduced firmness of the beans more than soaking or blanching of the whole beans. Antioxidant activity was lowest (3260 TE(3)100 g) in cream-colored beans and highest (16,600 TE/100 g) in brown-colored beans. The tannin contents of unprocessed cream-colored beans and dehulled wet-processed marble variety were not significantly different (p > 0.05). The levels of tannins in the marble variety were reduced by blanching for 40 min (19.2%), soaking for 12 hr (16.0%), dehulling (72.0%), dehulling and blanching (88.8%). The whiteness of bean flours was increased significantly by dehulling, slightly by wet-processing of marble variety, and reduced significantly by wet-processing of cream-colored beans.

Classification of white marble varieties by monocrystal X-ray diffraction

Classification of white marble varieties by monocrystal X-ray diffraction

PETROGRAPHIC AND ISOTOPIC CHARACTERIZATION OF THE MARBLE OF THE ISLAND OF TINOS (GREECE)*

Most outcrops of good‐quality crystalline marble in Mediterranean countries were exploited in Greek and Roman times. Hence, a wide variety of marble is now found in archaeological excavations. The precise determination of the provenance of a marble object is of great archaeological importance, and is now mostly obtained by coupling the petrographic study of a thin section with the analysis of the C and O stable isotopes, or by stereomicroscopy and EPR. The existing databases are considerable but still insufficient, because our knowledge about and study of ancient Mediterranean quarries remain incomplete. The contribution of this research is to add new petrographic and isotopic data on small quarries on the Greek island of Tinos that were exploited in antiquity. This marble belongs to the same geological horizon; it is quite pure, sometimes dolomitic and characterized by a low‐T, high‐P metamorphism that produced a limited recrystallization (MGS varying from 0.64 to 2.50 mm) on marine limestone protoliths. The petrographic features are quite distinctive: the fabric is strongly lineated and often stressed; and the accessory minerals are ubiquitary quartz, ore minerals, graphite and muscovite. As far as the isotopic data are concerned, δ13CPDB varies from 1.1 to 2.7, and δ18OPDB from −1.7 to −11.4. Both the features and the data have been compared with those of similar marbles used in antiquity, showing that their combination mirrors the fingerprint of the Tinos marble.

Discovering the stone heritage of southern Italy: technical properties of the Mondragone marble from Campania region

The results of the geological characterization of an old stone building in southern Italy, are presented here. The Mondragone marble is a slightly metamorphosed carbonate rock, which was widely employed as monumental stone in the 18th century Royal Palaces of Naples and Caserta. In this paper, for the first time, this rock has been investigated with a thorough laboratory testing program, aimed at defining its mineralogical, physical and mechanical parameters. The two most important varieties of Mondragone marble were separately tested: the yellow and grey marbles (hereafter, YM and GM, respectively). The results obtained from physical tests (open porosity, dry density, specific gravity, water absorption coefficients, ultrasonic velocity) did not show marked differences between the two materials; in contrast, the mechanical strength tests (uniaxial compressive strength, point load strength, flexural strength) showed better behaviour of YM than for GM. After a tentative comparison with other well known carbonate rocks from Italy, some considerations on the response of Mondragone marble to local weathering were conducted. In particular, the weathering typologies were related to the particular texture of the brecciated marble and the different strength resistances displayed by the various constituents of the rock.

Exsolution of Dolomite from Calcite

Calcites from a variety of marbles have been investigated by single-crystal X-ray techniques. Most of the specimens were relatively high-grade metamorphic carbonates, from amphibolite and granulite facies rocks. The typically clouded calcite of these rocks commonly contains dolomite, revealed by the X-ray photographs but not always observed under the microscope. This finely disseminated dolomite is in the same crystallographic orientation as the host calcite and is almost certainly an exsolution product. An oriented intergrowth of dolomite in calcite was produced in the laboratory. The original material was an echinoid test made up of spongy but single-crystal calcite with approximately 10 per cent $MgCO_3$ in metastable solid solution. This amount of Mg is stable in calcite only at temperatures well above 600° C; therefore exsolution of some of the Mg as dolomite took place when the sample was heated under $CO_2$ pressure at 500° C. The host magnesian calcite retained its identity as a single crystal, an...