Quartzite Stones Research Articles

Study of the Determination of Three-Point Flexural Strength Loading in Resin and Reinforcing Ornamental Stones

Theoretical framework: Brazil is one of the world's largest producers of ornamental stones, and is therefore the richest country in granite diversity in the world. Improvements in processing and production techniques have been developed over the years to add value to the final product. The resistance of stones is a preponderant factor for their application in certain environments. Some stone industries try to improve the resistance of the material by resining or reinforcing (resin plus fiberglass mesh) on their material. Method/project/approach: the work studied the behavior of resined and reinforced stones (resin plus fiberglass mesh). three-point flexural strength tests were carried out on pegmatite stones and quartzites. They were divided into groups with just resin and others with resin plus fiberglass mesh. Results and conclusion: The results showed that in the group of Pegmatite stones it was possible to obtain a gain of up to 44% in material resistance when resined and reinforced. However, the Quartzites did not have a significant gain, in some cases they obtained a lower value when reinforced. Only one of the quartzites achieved a 14% gain in resistance. Therefore, it is necessary to carry out a preliminary study with laboratory tests before resining and reinforcing the ornamental stones for sold. Research implications: Compare the three-point flexural strength between samples of pegmatic and quartzite stones and evaluate the resistance of reinforced (resin plus fiberglass mesh) and resin (resin) stones. Originality/value: analyze the influence of resin and fiberglass mesh on the three-point flexural strength of ornamental stones.

The Chronology of Early Human Settlement in Three Gorges Region, China—Contribution of Coupled Electron Spin Resonance and Uranium-Series Dating Method

The Three Gorges region (TGR) located in the geographic center of China, is a transition zone between mountain and plain areas, and a probable migration corridor for hominins and other mammals between South and North China. Detailed chronological information of paleoanthropological evidence in this area could help us better understand the human evolution in East Asia. The OSL and U-series dating methods are two conventional dating methods generally adopted to date such sites; however, their applications were limited by the dating range—restricted to several hundred of millennia and ambiguous stratigraphic relationship between the archaeological remains and the dating target materials. Cosmogenic nuclide burial dating of quartzite stone artifacts and coupled electron spin resonance and uranium series dating (ESR/U-series) of fossil teeth have the potential to date Early–Middle Pleistocene hominin sites in Asia and were applied increasingly in China in recent years. However, the application of cosmogenic 26Al/10Be burial dating is limited in TGR because most sites are dominated by limestone, leading to the scarcity of the quartz component. In this case, the coupled ESR/U-series method plays a more important role in the establishment of the chronology of human settlement. In TGR, by using the coupled ESR/U-series method, we have dated seven important Early and Middle Pleistocene hominin settlement sites, including Longgupo, Jianshi, Yunxian, Meipu, Bailongdong, Changyang, and Yumidong sites. Based on our dating results, we propose that hominins were settled in TGR probably from the early stage of Early Pleistocene (∼2.5−2.2 Ma) at the Longgupo site to the late Middle Pleistocene to Late Pleistocene of the Yumidong site (∼274−14 ka) and very likely to spread to other parts of East Asia during this time period. In view of the potential of coupled ESR/U-series dating on fossil teeth from the hominin sites in the TGR, future work may consider the micro damage or non-destructive analysis of enamel fragment with the ESR method and laser ablation ICP-MS techniques that will make possible the direct dating of precious human fossils in China.

Comparison between Synthetic and Biodegradable Polymer Matrices on the Development of Quartzite Waste-Based Artificial Stone

The development of artificial stone from the agglutination of polymeric resin using industrial wastes can be a viable alternative from a technical, economic, and sustainable point of view. The main objective of the present work was to evaluate the physical, mechanical, and structural properties of artificial stones based on quartzite waste added into a synthetic, epoxy, or biodegradable polyurethane polymer matrix. Artificial stone plates were produced through the vacuum vibration and compression method, using 85 wt% of quartzite waste. The material was manufactured under the following conditions: 3 MPa compaction pressure and 90 and 80 °C curing temperature. The samples were characterized to evaluate physical and mechanical parameters and microstructure properties. As a result, the artificial stone plates developed obtained ≤0.16% water absorption, ≤0.38% porosity, and 26.96 and 10.7 MPa flexural strength (epoxy and polyurethane resin, respectively). A wear test established both artificial quartzite stone with epoxy resin (AS-EP) and vegetable polyurethane resin (AS-PU) high traffic materials. Hard body impact resistance classified AS-EP as a low height material and AS-PU as a very high height material. The petrographic slides analysis revealed that AS-EP has the best load distribution. We concluded the feasibility of manufacturing artificial stone, which would minimize the environmental impacts that would be caused by this waste disposal. We concluded that the production of artificial rock shows the potential and that it also helps to reduce environmental impacts.

Adult and juvenile bearded capuchin monkeys handle stone hammers differently during nut‐cracking

Wild bearded capuchin monkeys (Sapajus libidinosus) habitually use stone hammers to crack open palm nuts and seeds on anvils. This activity requires strength, balance, and precise movement of a large stone with respect to the item placed on an anvil. We explored how well young monkeys cope with these challenges by examining their behavior and the behavior of adults while they cracked palm nuts using a stone. Using video records, we compared actions of six juvenile (2-5 years) and six adult (7+ years) wild monkeys during their first 20 strikes with one unfamiliar ellipsoid, quartzite stone (540 g), and the outcomes of these strikes. Compared with adults, juveniles cracked fewer nuts, performed a more diverse set of exploratory actions, and less frequently placed one or both hands on top of the stone on the downward motion. Adults and juveniles displayed similar low frequencies of striking with a slanted trajectory, missing the nut, and losing control over the nut or stone after striking. These findings indicate that young monkeys control the trajectory of a stone adequately but that is not sufficient to crack nuts as effectively as adults do. Compared with juveniles, adults more quickly perceive how to grip the stone efficiently, and they are able to adjust their grip dynamically during the strike. Young monkeys develop expertise in the latter aspects of cracking nuts over the course of several years of regular practice, indicating that perceptual learning about these aspects of percussion occurs slowly. Juvenile and adult humans learning to use stones to crack nuts also master these features of cracking nuts very slowly.

On the impacts of grain refinement and strain-induced deformation on three-body abrasive wear responses of 18Cr–8Ni austenitic stainless steel

The concept of phase reversion annealing involving cold deformation of metastable austenite to strain-induced martensite, followed by annealing was adopted to obtain fine grained 18Cr–8Ni austenitic stainless steel. The primary objective of the present study was to elucidate the wear performance of fine-grained austenitic stainless steel through three-body abrasive wear tests at room and high temperatures and compare with the coarse-grained counterpart. The quartzite stones (quartz content over 90 wt%) with diameter 5–15 mm and hardness of 1100HV were used as the abrasive in three-body abrasive wear tests. The study demonstrated that the microstructure consisting of near defect-free and equiaxed fine austenite grains with high yield strength and elongation exhibited superior wear resistance at high temperature (250 °C), which is attributed twinning induced plasticity deformation in fine austenite grains. The wear mechanism varied as a function of distance from the center of the steel sample and was characterized by microploughing and microcutting.

Hatshepsut and the Apis Race: New Quartzite Relief Fragments from Dra’ Abu el-Naga

The reconstruction of a scene sculpted on some quartzite stone fragments discovered recently at Dra’ Abu el-Naga and dating from the reign of Hatshepsut is the subject of this paper. The relief resembles the scenes known from the Red Chapel at Karnak and seems to be a part of the wdi sx.t ritual performed on the occasion of the Opet and / or Valley Festivals.

The Planning and Orientation of the Rego da Murta Dolmens (Alvaiázere, Portugal)

During the excavation of Rego da Murta Dolmen I, a structure belonging to a megalithic cluster in central Portugal, a number of small sub-quadrangular quartzite stones were found embedded within a layer below that of the deepest orthostat. In this paper, we report on these findings and highlight three key features of these small stones, namely their location relative to the dolmen’s plan, the distances between them, and their orientations. We suggest the quartzite stones could have been markers used in the planning of this megalithic structure. In addition, we analyse the orientations of the two main structures of the cluster (Dolmen I & Dolmen II), which are reflected by the orientation of the quartzite stones. We tentatively suggest potential landscape and skyscape alignments for their orientations, including three hypotheses for the observed differences in orientation between the two.

Influence of Quartzite Residues on the Strength of Added Red Clay Ceramics

The incorporation of industrial residues into red clay ceramics has in past decades been used not only as a search for the alternative use of lower cost raw-materials but also an environmentally correct way of destination of polluting wastes. This work had as its objective to study the influence of incorporation of a quartzite stone residue on the mechanical strength of a red clay ceramic. Clay bodies were prepared with up to 40 wt% of the residue. These clay bodies were then uniaxially press-molded and sintered at 800 and 1050oC. The strength was evaluated by three points bend tests. The microstructural analysis was conducted by means of both optical and scanning electron microscopes. A tendency for decreasing the strength was found with the amount of incorporated residue. This was a consequence of the inert characteristic of the quartz, which is the predominant mineral in the quartzite stone, as well as the possible effect of cracks nucleated during the quartz allotropic transformation.

Strength Characteristics of Hand-Quarried Partially-Weathered Quartzite Aggregates in Concrete

The use of hand-quarried weathered quartzitic aggregates as the coarse component of concrete was investigated. Samples of hand-quarried quartzite aggregates exhibiting different degrees of weathering were evaluated in quality and their suitability as coarse component of concrete. The 7, 14, 28 and 56 day compressive strengths were obtained from 100mm concrete cube samples prepared with the weathered aggregates in 1:1:2, 1:1.5:3, 1:2:4 and 1:3:6 concrete mixes and different water: cement ratios 0.45, 0.5 and 0.6. Modulus of rupture beams were tested aged 28-days. Control samples were also tested for compressive and tensile strengths using sound granite aggregates obtained from a commercial quarry. The quality tests showed very little difference between the un-weathered quartzite aggregates and the sound granite aggregates. The weathered quartzite aggregates except the highly weathered grade were found to have properties that met specification requirements for concrete. However, the partially weathered aggregates were marginal in quality and had high water absorption values. The 28-day compressive strength of the partially weathered quartzite concrete averaged 86% of the granite. It is concluded that except when the degree of weathering is very high, the partially weathered quartzite stone could be used as coarse aggregates in concrete that would be subjected to low stresses.

Changes of porosity due to weathering in quartzites and slates of a Raña profile (Montes de Toledo, Central Spain)

Ranas are alluvial fan deposits of Plio-Pleistocene age that form the piedmont platforms around the mountains in the interior of the Iberian Peninsula. They are composed of cobbles, pebbles and gravels of quartzite and some quartz, all embedded within a clayey matrix displaying striking changes in hues due to hydromorphism. Beneath these platforms, the Hercynian basement is consistently deeply weathered. In the profile of the Rana, the quartzite stones located into the clayey horizon have a weathering rind that is whitish to ochre in colour, in contrast to the dark reddish hue of those located within the leaching horizon, just below the land surface. These differences are related to changes in the physical properties (e.g., bulk density and porosity), mineralogy (presence of oxyhydroxides) and weathering processes that have taken place in the profile. Such processes have led to the corrosion and replacement of the quartz grains by the iron oxyhydroxides. The main cause is the dramatic changes in the water regime occurring in the pores at the surfaces of the quartzite stones. Due to weathering the slates outcropping beneath the Rana have undergone important release of matter (ca. 30%), together with changes in the mineral association, with a progressive reduction in the component of the unweathered slates and an increase in new minerals (smectites, kaolinite and iron oxyhydroxides) upwards.

El impacto de los conjuntos de trilleros en el registro paleolítico de la Meseta. Una aproximación etnoarqueológica

En el siguiente artículo se plantea la problemática que conlleva para el estudio del Paleolítico muchos depósitos líticos de carácter etnográfico y época histórica que se confunden con el registro arqueológico más antiguo. La principal aportación de este trabajo es la sistematización del proceso de elaboración de piedras de trillo en cuarcitas, y la caracterización geológica y arqueológica de estos conjuntos líticos en el territorio de Segovia.

A Pictish burial and Late Norse/Medieval settlement at Sangobeg, Durness, Sutherland

Salvage excavation was carried out on an archaeological site, discovered during the North Sutherland Coastal Zone Assessment Survey in 1998, in dunes at Sangobeg, near Durness in northern Sutherland. The excavation, conducted in 2000, uncovered the fragmentary remains of probable Norse-period settlement, including stone walling, a hearth and occupation deposits that had been truncated by erosion. Sealed beneath the Norse-period remains was the burial of a child of indeterminate sex, aged between 8–10 years, who had been placed in a flexed position on a bed of quartzite pebbles and covered with a mound of clean sand, capped with larger quartzite stones. The burial was dated by radiocarbon to 170 cal BC–cal AD 30 (GU-12535).

The soils and ages of the “raña” surfaces related to the Villuercas and Altamira mountain ranges (Western Spain)

Summary The soils of “rana” surfaces related to the “Sierra de las Villuercas” and the “Sierra de Altamira” (Western Spain) were studied with reference to vegetation cover and geomorphic position. These soils were highly weathered, with kaolinite dominant in the clay fraction and almost no weatherable minerals in the sand fraction. Iron oxides were segregated in some of the horizons giving a formation of “pseudoplinthite”. This high degree of weathering and the patina of their quartzite stones are comparable to those of soils developed on the oldest ran˜a surfaces studied in Central Spain. The soils classified as Palehumults and Palexerults are given, tentatively, a Middle-Upper Pliocene age.