G.E. Christidis

G.E. Christidis
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G.E. verified their affiliation via an institutional email.
Verified
G.E. verified their affiliation via an institutional email.
Technical University of Crete | TUC · Department of Mineral Resources Engineering

B.Sc, M.Sc, Ph.D

About

147
Publications
135,638
Reads
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3,333
Citations
Additional affiliations
December 1998 - present
Technical University of Crete
Position
  • Professor (Full) Economic Geology-Industrial Mineralogy
Education
November 1989 - July 1992
University of Leicester
Field of study
  • Economic Geology-Industrial Minerals (Clays)
October 1988 - September 1989
University of Hull
Field of study
  • Industrial Mineralogy
October 1983 - July 1987

Publications

Publications (147)
Article
Full-text available
The experiments presented here are based on the reconfiguration of an ancient medicine, Lemnian Earth (LE) (terra sigillata, stamped earth, sphragis), an acclaimed therapeutic clay with a 2500-year history of use. Based on our hypothesis that LE was not a natural material but an artificially modified one involving a clay-fungus interaction, we pres...
Poster
Full-text available
Several vascular plants produce silicate, calcium carbonate, and calcium oxalate phases in inorganic components of the plants known as phytoliths (SiO2.nH2O), through biomineralisation. Additionally, smaller amounts of strontium oxalate, strontium sulphate, and barium sulphate phases, among others, have been reported in various plants. Although phy...
Poster
Full-text available
The study assesses the palaeoenvironmental significance of coastal and shallow submarine deposits through the detailed characterisation and absolute dating of beachrock. The physicochemical composition of beachrock deposits provides valuable insights into the sediment types present during beachrock formation over time. The dating technique used was...
Poster
Full-text available
Biogenic silica (SiO2·nH2O), particularly in the form of microscopic phytoliths plays a crucial role in advancing archaeoenvironmental research by providing insights into plant-human interactions and broader ecological dynamics. Phytoliths (opal-A), formed through biomineralisation in terrestrial plants, especially grasses, are composed of durable...
Poster
Full-text available
This research provides a comprehensive examination of coastal and shallow submarine deposits through the detailed study of beachrock formations. Employing advanced analytical techniques, including X-ray powder diffraction (XRD), wavelength-dispersive X-ray fluorescence spectrometry (WD-XRF), and scanning electron microscopy with energy-dispersive s...
Article
Full-text available
The rheological properties of three Na-activated, trioctahedral Mg-bentonites (hectorite clay from the CMS Source Clay Project repository, saponite clay from Spain and stevensite clay from Rhassoul, Morocco) and a sepiolite clay from Greece were examined after dynamic ageing at temperatures up to 230°C. The 5% w/v suspensions were prepared by dispe...
Article
Montmorillonite (Mt) is a ubiquitous swelling clay mineral and major component of soft rocks, sediments, and soils with an inherent capability to sorb metal cations. This unique feature renders Mt important for the enrichment and mobilization of environmentally important metal cations, retardation of heavy metals and radionuclide ions, the evolutio...
Article
Full-text available
Layer charge is an important property of 2:1 phyllosilicates originating from isomorphic substitutions in the structure, from vacancies in the octahedral sheet and from unsatisfied bonds at the edges of the crystals. It is of particular interest in the case of smectites because it affects important properties of this mineral. Several methods have b...
Conference Paper
Full-text available
This study investigates key parameters which determine the development of strength in lime-pozzolana pastes. The percentage and the reactivity of amorphous matter, the bulk mineralogy and texture of the samples and the grain size distribution of the materials, are the most significant parameters that affect the mechanical behaviour of the pastes. P...
Article
Full-text available
Sediments from the ST5 deep-sea bottom core collected from the south-east Aegean Sea between Symi and Tilos islands, Greece, were examined by quantitative mineralogical analysis and geochemical analysis to infer provenance and palaeoenvironmental control over sediment deposition. The mineralogical composition comprises carbonates (mainly calcite an...
Article
Full-text available
Six ordinary Portland cement (OPC) clinkers and one white cement clinker were analyzed with the Rietveld method, using ZnO internal standard (IC), to determine the presence of amorphous matter (AM). All clinkers contain abundant AM and have lower silicate phase contents when compared with the same clinkers analyzed without IC, whereas the abundance...
Article
Full-text available
A set of samples with different textures from the sedimentary Fe–Ni deposits of Central Euboea, Greece, were studied with XRD and SEM-EDS to investigate the relationships between phyllosilicates present. The deposits are characterized by the coexistence of smectite, corrensite, R0 mixed-layer chlorite-smectite and discrete chlorite, which indicates...
Article
Montmorillonite, a ubiquitous clay mineral, has been engineered into a variety of porous and nanostructured catalysts, owing to its peculiar layered structure with characteristic surface and intercalation chemistry. Such a class of catalysts have continuously received considerable attention in both science and industry. This review examines recent...
Article
Full-text available
This article studies the geological structure, mineralogical composition, genesis and industrial properties of bentonite of the 10th Khutor deposit (Republic of Khakassia, Russia). The deposit is confined to the coal-bearing formation of Carboniferous age and is one of the main sources of bentonite for the metallurgical and foundry industries in Ru...
Article
Full-text available
Mineral compounds, as pigments and therapeutics, appeared regularly in the technical and medical texts of the Greco-Roman (G-R) world. We have referred to them as ‘G-R medicinal minerals’ and we suggest that despite their seeming familiarity, there are actually many unknowns regarding their precise nature and/or purported pharmacological attributes...
Article
Smectites affecting water and soil exchangeable cations, especially potassium and ammonium related to plants, are common swelling clay minerals in sediments and paleosols that can record paleoenvironmental and paleoclimatic information. Paleoenvironmental and paleoclimatic interpretations are potentially ambiguous, because smectite minerals may hav...
Article
Full-text available
Phytoliths from two different wheat species, Triticum monococcum and Triticum durum, known for their long-lasting significance to humans, were studied by a multi-analytical approach. Characterisation of phytoliths assisted in understanding their microstructure and behaviour after extraction from plants by the dry ashing and the wet ashing methods....
Article
This study evaluates the rare earth element (REE) geochemistry in altered trachyandesitic ignimbrites, tuff and lava flows in the Hashtjin area by assessing chondrite-normalizedREEpatterns and Y/Ho geochemical ratios. Modifications in theREEpatterns took place along altered fault zones that were affected by hypogene and supergene alterations. The p...
Article
Chitosan-clay bionanocomposites were prepared from chitosan biopolymer solutions and four different smectites (SAz-1 and SWy-2 montmorillonites, SBId-1 beidellite and NAu-1 nontronite), and the effect of layer charge and charge distribution on the formation of bionanocomposites was examined. The intercalation of the chitosan in the homoionic Na⁺-sm...
Article
Full-text available
A great variety of fine grained industrial rocks, which are valued by the industry contain variable amounts of amorphous or poorly crystalline matter, which is not easily detectable by the conventional mineralogical analysis methods based on X-ray diffraction (XRD). The quantification of amorphous matter in industrial rocks is a major task because...
Article
Full-text available
Medicinal earths are an important and yet, so far, little scientifically explored archaeological resource. They are almost always identified by their source locality. Our work over the last few years has focused on their chemical and mineralogical characterization and their testing as anti-bacterials. This paper presents the results of the mineralo...
Article
The addition of clay minerals in drilling fluids modifies the dispersion's viscosity. In this article, scientific advances related to the use of clays and clay minerals (bentonite, palygorskite, sepiolite and mixtures of clay minerals) in drilling fluids are summarized and discussed based on their specific structure, rheological properties, applica...
Article
Ethnopharmacological relevance Medicinal Earths (MEs), natural aluminosilicate-based substances (largely kaolinite and montmorillonite), have been part of the European pharmacopoeia for well over two millennia; they were used generically as ‘antidotes to poison’. Aim of the study To test the antibacterial activity of three Lemnian and three Silesi...
Article
The Westerwald region is one of the major ceramic clay mining areas of Germany. The mined clays were deposited on the weathered Rhenish massif during Eocene and Oligocene and were protected from erosion by a large alkaline basalt cover. Two Fe-rich bentonite layers exposed in quarries of the Eastern part of the Westerwald were investigated with X-r...
Article
The widespread Balıkesir bentonite deposits within the Miocene volcano-sedimentary units in western Anatolia have economical potential; they are important raw materials for the paper and bleaching industries in Turkey. No detailed geological, mineralogical, geochemical, or genesis characterizations of these bentonite deposits have been carried out...
Article
Surface plasmon resonance was employed for the in-situ investigation of film formation from aqueous dispersions of clay minerals on gold/water interface. High charge (SAz-1) and intermediate charge smectite (STx-1b) were studied for their ability to form stable clay films on gold surfaces and their adhesion kinetics at different concentrations was...
Article
Sediments from two deep-sea bottom cores from the Myrtoon basin in the SW Aegean Sea and Eastern Cretan Sea were examined by quantitative mineralogical and geochemical analysis to infer sediment provenance and its possible role in models of climatic conditions and palaeo-environmental control on sediment deposition. Both cores contain calcareous mu...
Article
Full-text available
This project seeks to recover and record the archaeological evidence associated with the extraction of sulfur (and perhaps other minerals as well) by James Stevenson, a Glasgow industrialist, from the volcanic island of Vulcano, Aeolian Islands, Italy, in the second half of the 19th century. This short preliminary report sets the scene by linking a...
Article
Full-text available
This project seeks to recover and record the archaeological evidence associated with the extraction of sulfur (and perhaps other minerals as well) by James Stevenson, a Glasgow industrialist, from the volcanic island of Vulcano, Aeolian Islands, Italy, in the second half of the 19th century. This short preliminary report sets the scene by linking a...
Article
Full-text available
This paper introduces a holistic approach to the study of Greco-Roman (G-R) lithotherapeutics. These are the minerals or mineral combinations that appear in the medical and scientific literature of the G-R world. It argues that they can best be described not simply in terms of their bulk chemistry/mineralogy but also their ecological microbiology a...
Conference Paper
Full-text available
Sediments from three deep-sea bottom gravity cores in the Myrtoon Basin SW Aegean (KIM4), Creta Sea South Aegean (TI13) and SE Aegean Sea (ST5), Greece, were examined by quantitative mineralogical and geochemical analysis in order to discuss the factors controlling its geochemistry and obtain data that might be used as destination and transport tra...
Article
Full-text available
The clay mineralogy of the sedimentary Fe-Ni deposit of Agios Ioannis and a Ni lateritic profile from Pavlos, both in Lokris area, Greece, is investigated. The clay fraction of samples from Agios Ioannis consists mainly of Fe-rich chlorite and Fe-smectite, with minor serpentine, hematite and goethite. Locally, disordered talc (kerolite and/or pimel...
Article
Full-text available
Stevensite is a Mg-trioctahedral smectite with layer charge stemming from vacancies in the octahedral sheet. In the present work we studied the thermal behavior of Jbel Ghassoul stevensite from Morocco, known as Ghassoulite or Rhassoulite, free of talc layers. The clay fraction of the material was separated by sedimentation, it was subsequently hea...
Conference Paper
Full-text available
Bentonite mining, blending and first stages of raw processing are usually planned based on physical properties and smectite content of the bulk material, in order to appoint a proper market destination. What if there was a structural feature from smectitic phases that could stablish feasibility for advanced and high added-value applications, right...
Article
The medicinal minerals of antiquity reported in Greco-Latin texts are now understood to consist primarily of lay-ered silicates, sulphates and metal oxides/sulphides, normally not in their natural state but following some processing. Recent microbiological work on layered silicates from some volcanic islands in the Aegean (Samos) and on samples of...
Article
Full-text available
Greece is a major bentonite producer, with Milos Island being one of the largest bentonite mining centres in the world. In addition to the bentonite deposits which are well known, various other occurrences exist in the islands of Chios and Samos, Eastern Aegean and in some areas of Thrace, in NE Greece. These bentonites are associated with volcanic...
Article
Full-text available
Layer charge (LC) is a fundamental property of smectite but its measurement remains challenging and tedious to apply on a high-throughput basis. The present study demonstrates that the position of a sharp, high-energy O–D stretching band of adsorbed D2O (νO–D, at ∼2686–2700 cm–1), determined by infrared spectroscopy, correlates with LC and provides...
Poster
Full-text available
The so called small theatre of Ambracia, the smallest of all ancient theaters revealed so far in Greece, is located in the centre of the contemporary city of Epirus, Arta. Recent excavation works carried out by the local Ephoreia of Antiquities, revealed the existence of a unique updraft kiln of the Byzantine period. A remarkable variety of ceramic...
Article
Full-text available
This Open Access (OA) special issue of Clay Minerals includes papers presented at the 7th Mid-European Clay Conference held on 16–19 September, 2014 in Dresden-Radebeul, Germany. Clay groups from eastern- and mid-European countries established in 2001 the first joint meeting called the “Mid-European Clay Conference” (MECC), to be held every second...
Article
Full-text available
The combination of intense solar radiation and soil desiccation creates a short circuit in the biogeochemical carbon cycle, where soils release significant amounts of CO2 and reactive nitrogen oxides by abiotic oxidation. Here we show that desert soils accumulate metal superoxides and peroxides at higher levels than non-desert soils. We also show t...
Article
Full-text available
A new model is proposed for analysis of the source clays used to create ceramics, based on geographic, petrographic, mineralogical, mineral-chemistry, and geochemical criteria. The development of this model became feasible after the discovery of a Pliocene volcanic clay horizon on NW Aegina Island, Greece. The volcanic clay contains smectite, mixed...
Poster
Full-text available
Cement industry is facing growing challenges in conserving materials and conforming to the demanding environ-mental standards. Therefore, there is great interest in the development, investigation and use of binders alternatives to Portland cement. Natural hydraulic lime (NHL) binders have become nowadays materials with high added value, due to thei...
Chapter
Full-text available
Industrial clays are very important raw materials which find numerous industrial and technological applications, including the production of materials with large added value such as nanocomposites, cosmetics, or pharmaceuticals. The versatile nature of clays is attributed to the presence of clay minerals, which impart significant physical propertie...
Article
Full-text available
A new method for identifying the trioctahedral smectites saponite, stevensite and hectorite is proposed in this study. The method is based on differences in the X-ray diffraction (XRD) patterns of the three smectites after (a) heating at 500°C for 90 min and (b) glycerol solvation of the Cs-forms of the smectites for 20 h. After heating at 500°C, w...
Poster
Most readers would agree on the fact that layer charge is the most determinant property from Smectites phases present in Bentonite deposits, to comprehend the overall interaction behavior of this materials for scientific and Industrial uses. Nevertheless, there is yet a lot to be discovered regarding diagenetic implications on magnitude and nature,...
Conference Paper
Clay suspensions are important constituents of drilling fluids. Although there are numerous publications on the rheological properties of single clay suspensions, there is limited information on mixed clay suspensions. In this study, the rheological behavior of four different bentonites mixed with Greek sepiolite has been evaluated. The parameters...
Article
Full-text available
Detailed multi-scale characterization of the kaolin quality and the controlling depositional environment is crucial for optimal quality upgrading and for prioritizing potential exploitation areas. In the present work, the quality of El-Tih kaolin, Egypt, was investigated using the chemical/mineralogical characteristics as well as the field observat...
Article
Full-text available
Zeolites are the main mineral components in altered volcaniclastic rocks ranging in age and composition. They form by alteration mainly of volcanic glass in various geological environments, under variable geochemical and temperature conditions. Proposed genetic models of zeolite deposits include weathering, diagenesis in open or closed hydrologic s...
Article
Full-text available
Industrial minerals and rocks are Earth materials utilized because of their characteristic physical and/or chemical properties and not because of their metal content and which are not energy sources. According to this definition they cover a broad spectrum of minerals and rocks which form at all geological environments. The relative importance of i...
Chapter
Full-text available
Clays have been used by man since prehistoric times. Initially they were used almost entirely in the fabrication of ceramics, nowadays they find numerous industrial and technological applications including the production of materials with large added value such as nanocomposites, cosmetics or pharmaceuticals. The term clay should not be considered...
Chapter
Full-text available
This volume covers the topics related to the 13th EMU School ‘Layered Mineral Structures and their Application in Advanced Technologies’. All of the selected topics, the school, and this volume are thus aimed at providing an in-depth knowledge of the complex field of layered materials, with an attempt to address several fundamental aspects, which r...
Article
Full-text available
The clay mineralogy of the sedimentary Fe-Ni deposit of Agios Ioannis and a Ni-lateritic profile from Pavlos, both in Lokris area, Greece, is investigated. The clay fraction of samples from Agios Ioannis consists mainly of Fe-rich chlorite and Fe-smectite, with minor serpentine, hematite and goethite. Locally , disordered talc (kerolite and/or pime...
Article
Full-text available
In this contribution we examine the rheological properties of palygorskite rich clays from the Ventzia Basin, W. Macedonia, Greece. The clays consist of palygorskite and/or dioctahedral Fe-rich smectite (nontronite) and quartz as main components, and serpentine, amphibole and sepiolite as minor constituents. The apparent and plastic viscosity and y...
Article
Full-text available
Bentonites are clay rocks consisting predominantly of smectite. They form mainly from alteration of pyroclastic and/or volcaniclastic rocks. Extensive deposits, linked to large eruptions, have formed repeatedly in the past. Bentonite layers are useful for stratigraphic correlation and for interpreting the geodynamic evolution of our planet. Bentoni...
Article
Full-text available
The validity of the structural formula (SF) method for calculation of layer charge of smectites is examined through re-interpretation of published data, which suggest that the SF method overestimates layer charge. The overestimation of layer charge by SF is based on assumptions about the permanent CEC (CECperm) of smectites i) on the association of...