Iron Ochre Research Articles

ICONS CONSERVATION AND PIGMENTS IDENTIFICATION OF THE SACRED ICONS PAINTER ANTONIOS AGORASTOS

The sacred icon painter Antonios Agorastos became known after the recording of his inscribed icons in Skopelos by Pavlos Lazaridis, covering a period of 30 years 1667-1703. The signed icons that we studied in Tyrnavos are the two icons of the Virgin Mary and Christ in the iconostasis of the church of Saint Anargyros on either side of the Beautiful Gate. The aim of the research is the study of the pigments of the hagiographer and the evaluation of other nonsigned icons. In a golden background, the Virgin Mary is depicted enthroned in the form of the Infant. She is depicted sitting frontally holding Christ in front of her. At the bottom right is an inscription with the painter's name, by the hand of Antonios sub deacon Agorastos Kritos (1668). Also, in a golden background, Jesus Christ is depicted enthroned in the type of Pantocrator. With his right hand he blesses and with his left he holds an open evangelist painting of holy icons. For the measurements of the pigments in the icons, the following techniques were used: a) Raman spectroscopy Thunder Optics - Gem Raman System with 532nm laser excitation, while before identification, the spectra were subjected to a procedure such as baseline correction, Savitzky - Golay smoothing - normalization and b) the XRF spectrometer Niton XLp 818 technique with an excitation source of 241 Αm. Analysis of Raman and XRF spectra was performed with the help of Spectragryph software. The identification of pigments using the two complementary techniques revealed the use of a variety of inorganic pigments such as lead white, copper green (verdigris), copper blue (azurite), for yellow (realgar), iron ochres (red and yellow) and cinnabar for the red colour.

Can X-ray Diffraction Distinguish Natural from Anthropogenic Hematite? Replication of the Conversion of Natural Goethite in Both Furnace and Campfire

Hematite, the mineral that gives color to bright red iron ochres, occurs naturally, but there is much evidence that early humans sometimes artificially produced hematite by heating a related mineral, goethite, in wood fires. This represents an important cognitive and technological advance in early human prehistory. Thus, there is a need to distinguish natural hematite from hematite generated by heating goethite in a wood fire. Measuring the line widths of powder X-ray diffraction (XRD) in hematite has been explored, and synthetic goethite heated in a modern furnace has been used as a model system for studying this process. We now show that to be an inappropriate model. Although chemically identical, natural goethite is physically different from and much more variable than goethite produced in a laboratory. Furthermore, by replicating the process using Stone Age technology, we show that heating goethite in a wood fire complicates the interpretation of XRD line widths of the resulting hematite. We conclude that strategies other than powder XRD are necessary to draw conclusions about the ancient processing of iron ochres.

Reduzierung von Versinterung durch optimierte Drainagebedingungen – Erkenntnisse eines Feldversuchs

AbstractA field test was carried out in Koralmtunnel in order to enhance process understanding and to optimize the drainage system in a tunnel section that is complex in terms of hydrochemistry, water inflow and mineral (calcareous scale, iron ochre) and biological (microbial mats) deposits. The field test comprised three test fields with different system components and flow characteristics. The development of critical waters and deposits was recorded by continuous measurements of relevant water and air parameters by means of autonomous sensors/data loggers. Furthermore, the components were ”forensically“ examined with respect to scale formation. The experiments show the crucial importance of gas exchange (CO2, oxygen ingress), filling level (flow geometry/regime), residence time of waters and water‐air interaction in the drainage system. The type, material consistency, and amount of scale and biofilms depend significantly on specific gradients. Floating scale crusts formed in stagnant sections, biofilms and iron ochre deposits of soft consistency formed at higher flow rates. Seepage packs and siphons turned out to be potential sediment traps with decreasing flow‐through with no access. Drainage hoses and dimpled membranes tend to be beneficial because they can prevent air exchange at relatively high flow rates. High CO2 partial pressure within these components (measured and modeled) inhibits carbonate precipitation. The drainage system is locally designed as a series of direct cross‐drains with simple flow paths, restricted air exchange, precautionary cleaning access, and optional water hardness stabilization (liquid conditioning).

Application of Earth Pigments in Cycloolefin Copolymer: Protection against Combustion and Accelerated Aging in the Full Sunlight Spectrum.

In this paper, we assess various natural earth pigments as potential colorants and stabilizers for ethylene–norbornene copolymer composites. Several cycloolefin copolymer (COC) composites colored with 2 wt% of a selected pigment were prepared using a two-step mixing method. The aging resistance of the polymer composites was investigated in terms of changes to their mechanical properties, following accelerated aging in the full sunlight spectrum (100, 200, 300, 400, and 500 h). Fourier-transform infrared spectroscopy (FTIR), surface energy measurements, and spectrophotometry were used to assess the color changes, surface defects, and morphology of the composites. Thermogravimetric analysis (TGA) was used to study their thermal stability. The combustion characteristics of the prepared COC composites were evaluated based on the microcombustion calorimetry test (MCC). The application of earth pigments resulted in interesting color changes and a significant improvement in the aging resistance of the COC-filled samples, as evidenced by higher aging factor values and lower carbonyl index parameters compared to the reference (COC). The best results were observed for hematite (HM), gold ochre (GO), and red ochre (RO). In addition, the application of earth pigments, especially iron ochre (IO) and red ochre (RO), in COC contributed to a significant reduction in the heat release rate (HRR) values, indicating improved flame retardancy. This research opens the possibility of producing colorful COC composites with enhanced photostability and reduced flammability for use in polymer applications.

Colouring of Pacific barkcloths: identification of the brown, red and yellow colourants used in the decoration of historic Pacific barkcloths

Barkcloth textiles made in the Pacific islands and collected by western explorers in the eighteenth and nineteenth centuries form part of many museum collections worldwide. Here high-performance liquid chromatography (HPLC) and X-ray fluorescence (XRF) were used on cloths that were highly coloured or pigmented specifically focussing on identifying the red, yellow and brown colorants. The cloths studied came from collections held at the Hunterian, University of Glasgow, the Economic Botany Collection, Royal Botanic Gardens Kew and the Centre for Textile Conservation and Technical Art History, University of Glasgow. HPLC analysis was carried out following a sequential extraction procedure to minimise changes to the colorants during extraction. A portable XRF was used so no invasive sampling was required. A small number of plant derived colorants were found, Morinda citrifolia, noni (morindin or morindone), Rubia tinctorum (madder), tree tannins and Curcuma longa (turmeric) plus an inorganic colorant, iron oxide. For 40 samples a single colorant was found while in the remaining 12 samples combinations of up to three colorants were found. Madder was found in only 2 samples on the same cloth. The morindone coloured samples were all red whereas morindin samples were both red and yellow. Morindin was used predominantly in combination with other colouring agents. A combination of iron ochre and organic colorant was found in 4 samples. These findings show that despite the numerous potential colorant sources for red, brown and yellow shades listed in the many accounts of historic barkcloth making, only five types of plant colourant and one inorganic pigment were found. There are a number of potential reasons for these findings. Some colours may have faded and so no longer appear coloured. It is also possible that, as some of these cloths were prepared specifically as gifts for visitors or for ceremonial uses, the makers used materials that they knew would retain their integrity over time. Perhaps, like artisans worldwide, experience had taught them that some colorants, although initially bright and vivid, faded over time.

Synthesis and characterization of iron and iron nitride microtubes obtained from biogenic iron oxide

With the aim to obtain iron tubular microstructures attractive for various applications, we have used a natural biogenic iron ochre as a raw material and explore various procedures and experimental conditions to achieve our goal. Our experiments included reduction, nitridation and characterization of microtubes derived from biogenic iron ochre. Various temperatures of reduction under streams of H2/N2 or NH3 were tested. Our results show that the tubular structure is maintained after reduction of the natural material under H2/N2. In addition, ammonia was not produced under our experimental conditions, and as expected, hydrogen reduced the material. However, the treatment under NH3 reduces the material and allows the incorporation of nitrogen into the structure of the solid yielding iron nitride microtubes. Reduced and nitrided microstructures were successfully obtained from natural biogenic iron ochre. A temperature of 500 °C seems to be suitable to expose the calcined biogenic iron ochre under H2/N2 for 4 h or under ammonia for 8 h to obtain reduced or nitrided microtubes, respectively. The stability of the tubular structure during reduction/reduction–nitridation is maintained under both treatments. Further interesting applications of this natural biomaterial could be envisaged.

Ancient Gold Mining at Ada Tepe, East Rhodopes, Bulgaria. Mineralogical Features of Au-Containing Fe-Oxides/Hydroxides from the Ada Tepe Gold Deposit. Their Significance in Clarifying the Ancient Gold Mining

Ada Tepe is the oldest known open-pit mine on the Balkan Peninsula for mining gold from host rocks. The mine probably started operation around 1500 BC and continued to function until the end of the 12th to the middle of the 11th century BC. The sedimentary and hydrothermally altered host rocks in the upper zone of Ada Tepe are usually of a grey or yellow colour or, in some places, yellow-brown. The rock pieces in the waste dumps are usually darker, with a red or red-brown coloration, which is obviously not connected to geological processes. It is suggested that the difference in colour between the host rocks and the fragments in the waste dumps are due to the phase transformation of minerals caused by the ancient miners using fire to fracture the host rocks in order to extract the gold ore. The majority of the analysed rock samples have a polyphase composition of goethite, hematite, schwertmannite, Au-Ag alloys, iron ochres, quartz and adularia. The phase diagnostics were performed by ore microscopy and powder X-ray diffraction (PXRD), morphological peculiarities were determined by scanning electron microscopy (SEM) while the thermal behaviour was investigated by differential thermal analysis and thermo gravimetric (DTA-TG) method. This paper will present the analytical results, which led to the conclusion that the difference in the coloration is due to the processes of transformation of nano-sized Fe3+ (oxy)hydroxides and (oxy)hydroxysulfate minerals caused by anthropogenic thermal processing.

Biogenic and bio‐structured inorganic materials in heterogeneous catalysis: a brief overview

AbstractThis mini‐review highlights some research results related to the production and application of biogenic and biomorphic materials in catalysis. Such approaches are of interest for the preparation of materials of unusual and well defined morphology, as well as the recovery of valuable resources from waste streams. Areas covered are the application of biogenic iron oxide occurring as a natural waste in the form of iron ochre which can cause issues in water management, the application of biogenic manganese oxide materials formed from manganese rich media (and therefore possibly playing a role in water remediation), the application of bacteria for the preparation of metal nanoparticles of potential relevance to precious metal recovery from waste streams and the application of natural biological materials as templates for biomorphic inorganic materials of controlled and unusual uniform morphology. © 2015 Society of Chemical Industry

Iron ochre-a pre-catalyst for the cracking of methane.

BACKGROUNDIron ochres are gelatinous sludges that can cause problems in terms of water management. In this work, the application of iron ochre obtained from a river has been applied to catalytically crack methane – another potential waste product – into two useful products, hydrogen and a magnetic carbon-containing composite.RESULTSThe powder X-ray diffraction (XRD) pattern of the iron ochre was found to be consistent with the expected 2-line ferrihydrite, and energy dispersive X-ray (EDX) analysis showed Fe to be a major component although some Si and Ca were present. The sample was observed to contain a fraction with a tubular morphology consistent with the presence of extra-cellular biogenic iron oxide formed by leptothrix. Upon exposure to methane at elevated temperatures, the material was found to transform into an active catalyst for hydrogen production yielding a magnetic carbon-containing composite material comprising filamentous carbon and encapsulating graphite.CONCLUSIONThe application of two waste products – iron ochre and methane – to generate two useful products – hydrogen and a magnetic carbon-containing composite – has been demonstrated. Furthermore, the ochre has been shown to comprise tubular morphology extra-cellular biogenic iron oxide which may be of interest in terms of other applications. © 2014 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

The Effectiveness and Feasibility of Using Ochre as a Soil Amendment to Sequester Dissolved Reactive Phosphorus in Runoff

Incidental losses of dissolved reactive phosphorus (DRP) to a surface waterbody originate from direct losses during land application of fertilizer, or where a rainfall event occurs immediately thereafter. Another source is the soil. One way of immobilising DRP in runoff before discharge to a surface waterbody, is to amend soil within the edge of field area with a high phosphorus (P) sequestration material. One such amendment is iron ochre, a by-product of acid mine drainage. Batch experiments utilising two grassland soils at two depths (topsoil and sub-soil), six ochre amendment rates (0, 0.15, 1.5, 7.5, 15 and 30 g kg−1 mass per dry weight of soil) and five P concentrations (0, 5, 10, 20 and 40 mg L−1) were carried out. A proportional equation, which incorporated P sources and losses, was developed and used to form a statistical model. Back calculation identified optimal rates of ochre amendment to soil to ameliorate a specific DRP concentration in runoff. Ochre amendment of soils (with no further P inputs) was effective at decreasing DRP concentrations to acceptable levels. A rate of 30 g ochre kg−1 soil was needed to decrease DRP concentrations to acceptable levels for P inputs of ≤10 mg L−1, which represents the vast majority of cases in grassland runoff experiments. However, although very quick and sustained metal release above environmental limits occurred, which makes it unfeasible for use as a soil amendment to control P release to a waterbody, the methodology developed within this paper may be used to test the effectiveness and feasibility of other amendments.

Field Trials of Low-cost Reactive Media for the Passive Treatment of Circum-neutral Metal Mine Drainage in Mid-Wales, UK

This paper addresses the ability of five low-cost reactive materials to remove Zn, Pb, and Cd from Fe-poor, circum-neutral pH metal mine water in Mid-Wales, UK. Compost, fly ash, waste shell material, iron ochre, and a mixture of blast furnace slag (BFS) and basic oxygen furnace slag (BOS) were used in a series of small-scale passive treatment cells to assess metal removal from mine drainage initially containing, on average, 23.5 mg/L Zn, 0.5 mg/L Pb, and 0.05 mg/L Cd. Trial treatment cells contained between 1.5 and 12 kg of reactive media, had a 15 min residence time, and treated a discharge of up to 1 L per minute. Fly ash from a peat-fired power station was found to be the most effective material for metal removal, with concentrations reduced to 0.02 mg/L Zn, 0.0069 mg/L Pb, and 0.0001 mg/L Cd from over 1,000 L of water (between 98.6 and 99.9% removal). The other materials initially achieved high levels of metal removal (between 75 and 99.9% Zn, Pb, and Cd removed); however, all of the materials were saturated with Zn after less than 200 L of water had been treated. Metal sorption ranged from 21.4 mg/g Zn for the peat fly ash to 0.0015 mg/g Cd for the compost and BOS/BFS slag. The results of the pilot-scale field trials can be scaled to demonstrate that a modest-sized fly ash treatment cell (2.6 × 2.6 × 1 m) in size would be sufficient to remove 90% of the total metal load (Pb, Zn, and Cd) from this 10 L/min mine water discharge for a 1 year period. Importantly this research demonstrates that passive treatment for metal mine drainage can comply with water quality directives but cannot be considered a ‘walk-away’ solution; it requires modest (potentially annual) maintenance.

Mitigation of methane emissions from constructed farm wetlands

Constructed wetlands are increasingly used for water pollution treatment but may also be sources of the greenhouse gas CH 4. The effect of addition of two potential inhibitors of methanogenesis – iron ochre and gypsum – on net CH 4 emissions was investigated in a constructed wetland treating farm runoff in Scotland, UK. CH 4 fluxes from three 15-m 2 wetland plots were measured between January and July 2008 in large static chambers incorporating a tunable diode laser, with application of 5 ton ha −1 ochre and gypsum in May. CH 4 fluxes were also measured from control and ochre- and gypsum-treated wetland sediment cores incubated at constant and varying temperature in the laboratory. Ochre addition suppressed CH 4 emissions by 64 ± 13% in the field plot and >90% in laboratory incubations compared to controls. Gypsum application of 5 ton ha −1 in the field and laboratory experiments had no effect on CH 4 emissions, but application of 10 ton ha −1 to a sediment core reduced CH 4 emissions by 28%. Suppression of CH 4 emissions by ochre application to sediment cores also increased with temperature; the reduction relative to the control increased from 50% at 17.5 °C to >90% at 27.5 °C. No significant changes in N removal or pH and potentially-toxic metal content of sediments as the result of inhibitor application were detected in the wetland during the study.

Evaluation of iron ochre from mine drainage treatment for removal of phosphorus from wastewater

Treatment of polluting discharges from abandoned coal mines in the UK currently produces ca 30,000 t y −1 of hydrous iron oxides (“ochre”), for which there is no major end-use, but which has previously been shown to have potential for removing P from wastewater and agricultural runoff. The efficiency of ochre for P removal from wastewater was investigated in experiments at two sites in the UK: Leitholm in Scotland and Windlestone in England. The three-year experiment at Leitholm involved diverting secondary-treated wastewater effluent through a trough which contained granular and pelletized ochre at different times. In the nine-month experiment at Windlestone, beds of ochre pellets in horizontal and vertical flow configurations were tested. The ochre treatment systems at Leitholm reduced influent concentrations of total P (TP) and TP mass by ca 80% and 50%, respectively, during optimal flow conditions, and achieved a removal rate of up to 65 ± 48 mg TP kg −1 ochre d −1. There was no detectable release of potentially toxic metals from the ochre during the experiments. P removal rates by concentration were inversely related to flow and declined during the different phases of the experiments, probably due to clogging. At Windlestone, higher removal rates up to 195 mg TP kg −1 ochre d −1 were achieved for short periods of time following cleaning of the experimental system. Ochre has considerable potential to remove P from wastewater in a multi-stage treatment system and has a lifetime estimated to be 10 times longer than other substrates tested for P removal.

Conditioning factors of iron ochre biofilm formation on geotextile filters

This paper presents a study of ochre formation on geotextile filters. Ochre is a substance found sticking to solid surfaces of drainage systems and may cause clogging. Ochre formation is discussed based on the new concepts of biofilm development. Ochre formation is the result of microbial colonization and its affinity to iron compounds naturally found in seepage water. The aerobic–nonaerobic interface in drainage systems is a very favourable locale for optimum development of iron bacteria. Laboratory studies were done to verify the influence of intrinsic characteristics of the geotextiles and environment on ochre formation. Because flow condition was not considered in the tests, however, these results may not represent real field performance of geotextile filters. Tests of biofilm formation were conducted in Erlenmeyer flasks containing culture mediums for iron bacteria and geotextile samples. Nonwoven polyester, nonwoven polypropylene, and woven polypropylene geotextiles were used in the tests. The study was performed considering different levels of iron concentration, available dissolved oxygen, and pH. Laboratory tests have shown the fundamental importance of iron bacteria activity, type of geotextile, and environmental conditions on ochre formation.Key words: ochre, clogging, filtration, biofilm, geosynthetics.

Evaluation of natural radionuclides at Um-Greifat area, eastern desert of Egypt

Air borne radiometric maps and remote sensing techniques were used to explore for the occurrence of radioactive materials. The previous techniques recorded radioactive mineralization for the first time along the NW–SE trending fault zones within the Miocene clastic-carbonate sediments. In the present study, gamma-ray spectrometry was used to confirm the presence of this mineralization. Concentrations of radionuclides, associated within the iron ochre at Um-Greifat area, have been measured, using a hyper-pure germanium spectrometer. The variation in concentration of radionuclides for the area under investigation can be classified into A, B and C regions of high, medium and low natural radioactivity. In region A, average concentration in Bq kg −1 has been observed to range from 1858 to 4062 for 238U, between 29 and 151 for 232Th, from 60 to 136 for 235U and between 46 and 409 Bq kg −1 for 40K. Radium equivalent activities (Ra eq) in addition to external and internal hazard indices ( H ex, H in) have also been determined. Ra eq varies between 1901 and 4307 Bq kg −1, which exceeds the permitted value (370 Bq kg −1) and H ex and H in are higher than 1. The high activity concentration within region A points to an environmental hazard, while regions B and C have less exposure effect on human beings.

An Egyptian Cartonnage of the Graeco-Roman Period

Technical and analytical studies were carried out on a late Graeco/early Roman Egyptian cartonnage from the University of Southern California (USC 9428). The structure of the object was visually examined, and the layers of textile and plaster were identified as linen, wood fibres of mixed origin, and a lime-based plaster. Using a combination of techniques, the pigments used to decorate the cartonnage were identified as minium, Egyptian blue, green earth, a copper proteinate green, a mixture of Egyptian blue and iron ochres, a mixture of green earth and Egyptian blue, orpiment, hydrocerussite, a lac dye and a carbon lamp-black. The discovery of previously unrecognized and apparently rare pigments, such as a copper proteinate pigment from 350 BC, suggests that there is still much work to be done on the use of pigments and the techniques of painting and cartonnage production.

Geochemistry of iron ochres and mine waters from Levant Mine, Cornwall : R. J. Bowell & I. Bruce, Applied Geochemistry, 10(2), 1995, pp 237–250

Geochemistry of iron ochres and mine waters from Levant Mine, Cornwall : R. J. Bowell & I. Bruce, Applied Geochemistry, 10(2), 1995, pp 237–250

Geochemistry of iron ochres and mine waters from Levant Mine, Cornwall

The geochemistry of metal-rich mine waters and mineral precipitates from the Levant mine, Cornwall, has been examined. Sulphide oxidation at Levant mine has produced a wide range of secondary sulphides, oxides, chlorides, sulphates and carbonates in a gossan environment. The mine waters display a wide variation in alkalinity, pH, chloride, sulphate, sodium, potassium and heavy metal content which can be explained by variable degrees of mixing between acidic, metal-rich, rock drainage waters and neutral to alkaline sea waters. Transition metals are soluble in the acidic mine waters with concentrations up to 665 mg/l Cu, 41 mg/l Zn, 76 mg/l Mn, 6 mg/l Co and >2500 mg/l total Fe. The production of acid rock drainage and leaching of metals can be related to sulphide oxidation. Where these metal-rich acidic waters mix with infiltrated sea water, neutralization occurs and some metals are precipitated (principally Cu). Where pools of mine drainage are stagnant native copper and cuprite are precipitated, frequently observed replacing iron pipes and rail tracks and wooden shaft supports, due to electrode potential differences. In these solutions, dissolved copper species are also reduced by interaction with wood-derived organic species. Precipitation of iron oxyhydroxides, caused by a pH increase, also occurs and leads. to coprecipitation of other metals, including Cd, Co, Ph, Mn, Ag and Zn, thus limiting the release of dissolved metals in solution from the mine. However, the release of suspended metal-rich ochres in mine discharge waters (with high Ph, Zn, Cd, Mn, Ni, Sn, Sb, As, Bi, Cu, Co and Ag) will still present a potential environmental hazard.

Environmental impact of former gold mining on the Orangi river, Serengeti N.P., Tanzania

The Orangi river is an important all-year source of water for wildlife in the northern part of the Serengeti National Park. At two points along the river in the Banagi area, tributaries draining the adit and tailings of the Kilimafeza mine impact the Orangi. The former Au-Cu mine is subject to occasional wet season flooding leading to the release of iron ochres from the adit and physical as well as chemical mobilization of tailings material. The unpolluted river chemistry is essentially Na-Ca-HCO 3 − and well-buffered. Drainage water; from the tailings are characterized by low pH (2.3) and high concentration of sulphate (up to 3280 mg/l), aluminium (275 mg/l), arsenic (324 mg/l), copper (125 mg/l), iron (622 mg/l), lead (21 mg/l), manganese (65 mg/l), and zinc (126 mg/l). Adit-drainage waters are typically of a lower pH (4.6) and have a lower concentration of sulphate (up to 1840 mg/l) and metals (up to 25 mg/l Al, 92 mg/l As, 42 mg/l Cu, 258 mg/l Fe, 9.6 mg/l Pb, 53 mg/l Mn, and 102 mg/l Zn). Mixing of these acidic waters with the alkaline river leads to rapid metal precipitation as Fe-ochre coatings on clastic sediment. This effect is more noticeable in the dry season. Consequently, although the tributaries draining the two sources are heavily contaminated, the effective buffering of the mine drainage waters restricts any potential pollution to within 1 km of the mine workings. Faecal coliforms show an antipathetic relationship to low pH and high metal conditions. The only mobile metals in the water outside this area are Mn and Zn and their contamination can be biologically monitored using a protozoan-based bioassay.

Inhibition of iron precipitation from field drainage water

SummaryIn field drainage waters, Fe(II) can be oxidized to Fe(III), which is precipitated as iron ochre. At a farm near Aberdeen, Scotland, ochre is precipitated both chemically and biologically. The precipitation was delayed using the antibiotic D-threo-chloramphenicol and Cu(II) ions. Iron deposition was delayed on glass slides coated with copper filings. It is suggested that the incorporation and slow release of substances which inhibit ochre formation, from drainage pipe material, would be a valuable method of controlling the ochre problem.