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Agate Creek is a world-class Australian fossicking area located in remote northern Queensland. Its beautiful agates and thunder eggs are sought by collectors worldwide, each one being unique. This article honours the lifelong work of Paul Howard on the Agate Creek locality, his collection and research which culminated in his 2005 book. The Agate Project (a high-resolution photo database of cut and polished agates for research and teaching) is proposed as a tribute to Paul Howard and other collectors who wish to take part in the project. [ABSTRACT FROM AUTHOR]

A personal narrative is presented which explores the authors experience of being agates are reported to be recovered from undisclosed desert locations by nomadic tribespeople, although due to the harsh desert environment.

The article discusses about evidence, quarrying and lithic reduction of Hole-in the- Wall lemon-yellow agate during the Palaeo-American Clovis era. Topics discussed include geothermal spring used to generate electricity, principal ancient workings of the Hole-in the-Wall and hand-digging and sieving of ancient quarry debris.

Agate gemstones occurring in the Mesoproterozoic volcanic rocks of the Priozersk Formation (PrF) within the Pasha–Ladoga Basin (Fennoscandian Shield, NW Russia) were investigated to characterize the mineral and geochemical composition of the agates and provide new information concerning their origin. Optical and scanning electron microscopy, EDS microanalysis, X-ray powder diffraction, X-ray fluorescence spectrometry, Raman spectroscopy, inductively coupled plasma mass spectrometry (ICP-MS), and C-O isotope analysis were used for the study. Agate mineralization appears mostly as an infill of fissures, cavities, gas vesicles in massive and vesicular basalts, lava-breccias. The mineral composition of agates is dominated by alpha-quartz (fibrous chalcedony, microcrystalline and macrocrystalline quartz), but it also displays abundances of calcite. The characteristic red-brownish agate's coloration is caused by multiple hematite inclusions distributed in an agate matrix. The study revealed the two phases of agate formation in the PrF volcanics, which are most likely controlled by two distinctly different fluids and/or their mixture. At first, agates appeared due to post-magmatic iron-rich fluids. The late hydrothermal activity was probably triggered by intrusion of gabbro-dolerite sill and resulted in the second phase of agate formation. We suggest that the late hydrothermal fluids remobilized the iron compounds from the crust of weathering underlying the PrF volcanics, which led to additional formation of vein agates and filling of gas vesicles with hematite-rich calcite/silica matter. [ABSTRACT FROM AUTHOR]

Introduction The majority of recent works accept that agates are formed at temperatures

Agate gemstones occurring in the Mesoproterozoic volcanic rocks of the Priozersk Formation (PrF) within the Pasha–Ladoga Basin (Fennoscandian Shield, NW Russia) were investigated to characterize the mineral and geochemical composition of the agates and provide new information concerning their origin. Optical and scanning electron microscopy, EDS microanalysis, X-ray powder diffraction, X-ray fluorescence spectrometry, Raman spectroscopy, inductively coupled plasma mass spectrometry (ICP-MS), and C-O isotope analysis were used for the study. Agate mineralization appears mostly as an infill of fissures, cavities, gas vesicles in massive and vesicular basalts, lava-breccias. The mineral composition of agates is dominated by alpha-quartz (fibrous chalcedony, microcrystalline and macrocrystalline quartz), but it also displays abundances of calcite. The characteristic red-brownish agate’s coloration is caused by multiple hematite inclusions distributed in an agate matrix. The study revealed the two phases of agate formation in the PrF volcanics, which are most likely controlled by two distinctly different fluids and/or their mixture. At first, agates appeared due to post-magmatic iron-rich fluids. The late hydrothermal activity was probably triggered by intrusion of gabbro-dolerite sill and resulted in the second phase of agate formation. We suggest that the late hydrothermal fluids remobilized the iron compounds from the crust of weathering underlying the PrF volcanics, which led to additional formation of vein agates and filling of gas vesicles with hematite-rich calcite/silica matter.

Brazil is one of the leading suppliers of colored agates, mostly of its extraction and processing carried out by artisanal miners. Dyeing is the principal method used for color alteration, and the long heating times account for most of the energy consumption. In this context, this study aimed to evaluate the implementation of a cold dyeing procedure, dispensing any need for dye solution heating, for the cases of organic dyeing with Rhodamine B and Crystal Violet. The results obtained indicated that using cold dyeing allowed obtaining coloring levels similar to those produced commercially. Also, for some cases, satisfactory color alteration could be achieved using dye concentrations lower than that conventionally used. The proposed cold dyeing process arises as a sustainable option for saving energy, reduce greenhouse gas emissions, decrease solvent losses, and enhance the income of artisanal and small-scale producers.

Agate was highly regarded in antiquity and through the early modern period; when sliced, images seemingly inscribed by nature could be identified on its surfaces, and its layered colours were exploited for cameo carving. However, agate is also widely recorded in the rough in contemporaneous natural history collections where the 'eye' that could be cut from the core was valued in Aristotelian medicine. Taking as its starting point the hitherto neglected 1622 correspondence about a piece of agate between Peter Paul Rubens and the French humanist Nicholas‐Claude Fabri de Peiresc, this essay brings together collecting, friendship and artistic production within a context of early mineralogy. Through an investigation of the material, tactile, aesthetic and para‐scientific attributes of agate, and drawing on further evidence from Rubens's life, I propose a sensibility shaped by a predilection for the lithic whose influence is discernible in the artist's work as more widely understood.

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Aims: Agate workers in Khambhat, India and their community members are exposed to high levels of silica dust and related diseases. Use of effective prevention practices remains low, prompting the need for effective interventions which increase the uptake of and investment in prevention practices. We sought: (a) to describe knowledge, self‐efficacy, and practices among a population of workers, their family members, and neighbors involved in or located close to agate processing; and (b) to explore which factors are related to use of prevention practices and willingness to invest in new dust control technologies. Methods: A community survey was conducted to measure demographics, occupation and financial factors, knowledge, prevention practices, barriers, risk perceptions, and efficacy beliefs. Descriptive statistics were used and, among agate workers, hierarchical logistic regression explored predictors of prevention practice use and willingness to invest. Results: Among 1120 respondents, approximately 44%, 35%, and 8% of workers, family members, and neighbors used prevention practices, respectively. Knowledge and risk perceptions were generally high, where efficacy beliefs were low. Workers who had high levels of education, worked at home, and had high efficacy beliefs were more likely to report using prevention practices and being willing to invest. Barriers to prevention practice use included financial barriers, and beliefs that prevention is ineffective and health is not at risk. Conclusions: Interventions and future research should be designed to engage the community to improve preventive behavior, and implement affordable and effective dust control interventions in the agate industry. [ABSTRACT FROM AUTHOR]

Agates with spectacular micro-structural features were found in volcanic rocks at several occurrences in the Saar-Nahe region (Germany). These agates include spirals of several tens up to several hundreds of μm in size within zones lacking the characteristic structural agate banding. A combined mineralogical study by polarising microscopy, scanning electron microscopy, cathodoluminescence microscopy and spectroscopy, and electron backscatter diffraction provided evidence that the spirals consist of well-ordered trigonal α-quartz, whereas the surrounding matrix is composed of strongly disordered or amorphous SiO2 phases. The quartz micro-crystals show a systematic rotation of the crystal orientation perpendicular to the direction of the spiral loops indicating helical growth. It is assumed that the spiral growth is initiated by dislocations with a screw component. The lacking symmetry of the strongly disordered or amorphous matrix initiated a curved development by a screw dislocation in a system far from equilibrium. The atoms/molecules are packed into spiral layers, which is energetically favoured in comparison with the incorporation into plane crystal faces. Such self-organisation growth and polymerisation initiated by a screw dislocation can produce variable spiral morphologies sometimes resembling living forms. [ABSTRACT FROM AUTHOR]

Agates of Paleoproterozoic volcanics (2100−1920 Ma) within the Onega Basin (Karelian Craton, Southeast Fennoscandia) were studied using optical and scanning electron microscopy, X-ray powder diffraction, X-ray fluorescence spectrometry XRF, laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), and C-O isotope analysis. Agate mineralization is widespread in the lavas gas vesicles, inter-pillow space of basalts, picrobasalts, basaltic andesites, as well as agglomerate tuffs. Agates are characterized by fine and coarse banding concentric zoning; moss, spotted, veinlet, and poor-fancy texture types were identified. Agate mineralization is represented by silicates, oxides, and hydroxides, carbonates, phosphates, sulfides, and sulfates. Among the silica minerals in agates only chalcedony, quartz and quartzine were found. The parameters of the quartz structure according to the X-ray diffraction data (well-develops reflections (212), (203), (301), large crystallite sizes (Cs 710–1050 Å) and crystallinity index (CI 7.8–10.3) give evidence of multi-stage silica minerals recrystallization due to a metamorphic (thermal) effect. The decreasing trend of trace element concentration in the banded agates from the outer zone to the core suggests a chemical purification process during crystallization. C-O isotope characteristic of agate-associated calcite reflects primary magmatic origin with the influence of hydrothermal activity and/or low-thermal meteoric fluids. Agates were formed under low PT-parameters and related to hydrothermal activity on the first stage of Svecofenian orogeny within 1780−1730 Ma. Thus, it can be believed that the temporal gap between continental flood basalts outflow and agate formation is about 190 Ma.

Agates from Płóczki Górne hosted by Permian basaltic rocks are predominantly made of length-fast chalcedony, and subordinately megaquartz and quartzine. Moganite occurs in traces mainly in transparent, outer, darker regions of white-grey coloured agates. Silica matrix of agates comprises a wide variety of solid inclusions represented by celadonite, plagioclases, hematite, goethite, barite, calcite, heulandite-clinoptyloite, nontronite-saponite, and Mn-dioxides (ramsdellite). Mineral phases are locally accompanied by black aggregations of carbonaceous matter, which gives a Raman signature of disordered carbon. These organic components were probably deposited from a hydrothermal fluids at low-temperature conditions and originated from sedimentary rocks found in the surrounding area of Płóczki Górne. The abundance of various SiO 2 phases, mineral inclusions as well as various micro-textures (colloform, comb, feathery, and jigsaw-puzzle) in agates resulted from physicochemical fluctuations of SiO 2 -bearing mineralizing solutions at various stages of these gems formation. Agates from Płóczki Górne formed during post-magmatic stage of basaltic host rocks evolution. Not only were the hydrothermal fluids enriched in silica, but also they contained other elements such as Na, Ca, Al, Mg, Mn, Fe, Ba, SO 4 , and CO 2 , which were mobilized from host rocks or surrounding area. [ABSTRACT FROM AUTHOR]

Gaseous and liquid fluids in agates (banded chalcedony--SiO2) of different localities were investigated systematically by thermogravimetry-mass-spectrometry within a temperature range from 25 to 1450 °C, for the first time. Chalcedony and macrocrystalline quartz from twelve agate samples were investigated, from Germany (Schlottwitz, St. Egidien, Chemnitz and Zwickau), Brazil (Rio Grande do Sul), Scotland (Ayrshire) and the USA (Montana). They originate from mafic and felsic volcanic rocks as well as hydrothermal and sedimentary environments. The results were evaluated regarding compounds of hydrogen with fluorine, chlorine, nitrogen, carbon and sulphur. Additionally, oxygen compounds were recognized with hydrogen, fluorine, nitrogen, sulphur and carbon. The nature of the compounds was identified based on their mass-charge-ratio and the intensity ratios of the associated fragments. Due to interferences of different compounds with the same mass-charge-ratio, only H2O, HF, NO, S, SO, CO3--as well as several hydrocarbon compounds (for example CO32- or CO)--could be properly identified. The main degassing temperatures were detected at around 500 and 1000 °C. Generally, a difference between quartz and chalcedony regarding the composition of their fluids could not be found. The results indicate a silica source for the agate formation from aqueous solutions but also a possible role of fluorine compounds. Additionally, CO2 and other fluids were involved in the alteration of volcanic rocks and the mobilization and transport of SiO2. [ABSTRACT FROM AUTHOR]

The German towns of Idar and Oberstein (now Idar-Oberstein) have a rich history of gem cutting and carving, notably in agate. The profession continues to be passed on from one generation to the next, as it has been for over five centuries. One of these families, the Drehers, has worked with gem materials for 13 generations. Gerd Dreher apprenticed gem carving with his father starting in 1955, while Gerd's son, Patrick, began his apprenticeship in 1988. While they carve individually, occasionally they work together as a team. The family creates fine carvings from agates and from single crystals of high-quality rough gem minerals. These unique pieces are extraordinarily detailed and utilize natural color zoning to achieve a remarkably lifelike effect. [ABSTRACT FROM AUTHOR]

Dehydration of silanol and molecular water in 60 agates from 12 hosts with ages between 23 to 2717 Ma has been investigated using desiccators and high-temperature furnace heating. There are wide differences in the water data obtained under uncontrolled and fixed atmospheric water vapour pressure conditions. After agate acclimatization at 20°C and 46% relative humidity, the total water (silanol and molecular) was determined in powders and mini-cuboids by heating samples at 1200°C. Agates from hosts < 180 Ma all showed a greater mass loss using powders and demonstrate that after prolonged high-temperature heating, silanol water is partially-retained by the mini-cuboids. Desiccator dehydration of powders and slabs shows that powder preparation can produce water losses; this is particularly relevant in agates from hosts < 180 Ma. The identified problems have consequences for water quantification in agate and chalcedony using infrared or thermogravimetric techniques. Mobile and total water in agate is considered in relation to host-rock age, mogánite content and crystallite size. Links are observed between the various identified water contents allowing comment on quartz development and agate genesis. The water data also supports previous claims that agates from New Zealand and Brazil were formed long after their host. [ABSTRACT FROM AUTHOR]

To solve the problems of high concentrations of Cr6+, SO2-4 and H+ in agate dyeing industrial wastewater and heavy pollution and high treating cost, single-factor and orthogonal experiments were conducted to determine the optimum particle size, the ratio of adsorbents dosing and hydraulic retention time based on peanut shells and scrap iron. Experiments, using five dynamic columns filled with the peanut shells, scrap iron and sulfate-reducing bacteria (SRB), were also conducted to determine the effect and mechanism of treating the wastewater. The results show that the best treatment effect was obtained when the diameter of peanut shells was 3 mesh, scrap iron being 60 mesh size, scrap iron and peanut shells with a ratio of 1:2, and hydraulic retention time being 24 h. By the comprehensive comparison of five groups of columns, the treating effect of column 4 was best, in which the removal rate of SO2-4 and Cr6+ was 30.17% and 88.36% respectively before adding the microorganisms, and 25.34% and 99.31% respectively after adding the microorganisms. The average of chemical oxygen demand (COD) release quantity was 62.11 and 513.75 mg·L-1, and the average effluent pH was 7.09 and 7.93 before and after addition of microorganisms respectively. In conclusion, peanut shells, scrap iron and SRB had a certain synergistic effect on treating agate dyeing wastewater. [ABSTRACT FROM AUTHOR]

Here we present a database of responses by South African agate and chalcedony to heat treatment. This will assist analyses of heated stone tools not only in South African archaeological sites, but wherever heated agate and chalcedony pieces were knapped. The minerals are abundant worldwide. To replicate potential heating methods during the Stone Age we placed some minerals in a wood fire, some under coals, and others were buried in sediments beneath fires. Thermal responses include lustrous flaked surfaces, pot lid fractures, semi-circular internal fractures, rough internal surfaces, and crazing. Aerobic heating is implied by pot lid fractures. To explain the thermal responses we analyzed the minerals using X-ray fluorescence, Raman spectroscopy, and carbon and sulfur analyses. Our chalcedony contains more water and impurities than agate, making it more vulnerable to thermal damage. Our method of combining field experiments with chemical analyses has global applications even though we expect that mineral components of agate and chalcedony will vary slightly in different parts of the world. [ABSTRACT FROM PUBLISHER]

The article features a Lake Superior agate that was discovered in Nodaway County, Missouri in 2019 and the question on the possible reasons why its one face is highly polished and showed colorful fortification bands of red, orange, yellow, white and black. Among the possibilities are it is water polished, it is a sacred ceremonial stone, and it is wind polished.

Agate nodules from Kerrouchen (Khénifra Province, Meknés-Tafilalet Region) in Morocco occur in Triassic basalts and reach up to 30 cm in diameter. Monocentric, banded agates—mainly in pastel pink, grey, white and yellow—with infiltration canals (osculum) are observed. Raman microspectroscopy revealed that the agates mainly consist of low quartz and subordinately moganite with distinctive 460 and 501 cm−1 marker bands, respectively. Linear mapping indicated that moganite mainly concentrates in grey zones of the monocentric agate nodules. The other types, polycentric and pseudostalactitic agates, are usually brown and red and contain minerals such as hematite and goethite. They form both regular and irregular mosaics rich in ornamentation. Occasionally, aggregates of copper sulphides or titanium oxides (rutile) can also be observed. These minerals are sometimes accompanied by carbonaceous material marked by 1320 and 1585 cm−1 Raman bands. It seems that formation of agates from Kerrouchen was induced by Si-rich and Fe-moderate fluids. Copper sulphides, rutile, and carbonates (possibly calcite) were most likely incorporated during post-magmatic processes. The origin of solid bitumen can be the result of hydrothermal or hypergenic processes. [ABSTRACT FROM AUTHOR]