Mines Repository (Colorado School of Mines)
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Crocoite
No full textPhotographed by Ron Wolf.Small needle-like prisms of dark orange crocoite on tan and grey matrix
Gold (roasted gold)
No full textPhotographed by Ron Wolf.Irregular rough lump of roasted gold and grey black matrix
Heulandite
No full textPhotographed by Ron Wolf.Translucent glassy white heulandite on grey brown matrix
Chalcedony after opal w. fluorite incl. (fluorescent)
No full textPhotographed by Ron Wolf.Gnarled mass of waxy white chalcedony after opal with purple fluorite (A0179-0326); two views of chalcedony after opal with fluorite: left view shows specimen in plain light; right view shows fluorescent properties of green under ultraviolet light (A0179-0327); white chalcedony after opal with purple fluorite, showing fluorescent properties of green under ultraviolet light (A0179-0328)
Mineral deposition in epithermal deposits formed through flash vaporization and implications for improved understanding of the Arista intermediate-sulfidation epithermal deposit in southern Mexico
No full textIncludes bibliographical references.2024 Spring.Bonanza-type epithermal deposits are formed within hundreds of meters of the paleowater table. They typically consist of banded veins and associated breccia, with quartz being the dominant gangue mineral. Petrographic evidence suggests that much of the quartz in these veins formed through recrystallization from a thermodynamically silica precursor. Recrystallization of this originally microspherical noncrystalline silica precursor resulted in vein textures that mask original relationships complicating reconstruction of the processes of ore deposition. The noncrystalline silica originally forming the bands in the bonanza-type ores is interpreted to have formed through rapid deposition from supersaturated liquids. The presence of ore mineral dendrites within the microspherical silica suggests that mineral deposition occurred at far-from-equilibrium conditions. Mineral deposition occurred during flash vaporization of the hydrothermal liquids. Fluid inclusion evidence from the Arista intermediate-sulfidation deposit in southern Mexico suggests that flashing along the major extensional structures controlling the location of the deposit occurred over ~1 km below the paleosurface. Deposition of high-grade ores over such a large vertical extent is inconsistent with models invoking that mineralization in the epithermal environment is formed by gentle boiling.
The study of the Arista intermediate-sulfidation epithermal deposit demonstrated that vein formation at this prolific polymetallic (Au-Ag-Zn-Pb-Cu) deposit was controlled by a relay ramp providing linkage between two adjacent extensional faults. The banded veins at Arista consist of quartz that formed through recrystallization of a noncrystalline precursor. The quartz hosts dendritic to massive sulfide minerals. Rare bands of quartz formed by deposition in open space are present. The veins crosscut felsic dikes and are also crosscut, themselves, by variably altered as well as unaltered dikes. The geological relationships suggest that igneous activity resulting in dike emplacement overlapped with the formation of the epithermal veins at ~18.5 Ma. Seismicity and dike emplacement may have been important in triggering rapid depressurization along the controlling structures, leading to repeated flash vaporization of the hydrothermal liquids and the formation of high-grade mineralization
Stibnite
No full textPhotographed by Ron Wolf.Vitreous blades of grey black stibnite, Stayton district, Hollister, San Benito County, California
Inverse design algorithm for arbitrary microwave circuits
No full textInverse design has attracted attention in recent years as an approach to synthesize complex electromagnetic structures, both in optical and microwave domains. As these structures grow in size and complexity, it becomes infeasible to solve the inverse problem with the aid of full-wave solvers. We present an algorithm that takes an arbitrary passive and reciprocal two-port microwave network defined by its S-parameter matrix, and breaks it down into an m-by-n grid of simpler two, three, and four-port interconnected networks. These blocks are simpler in nature, having fewer spectral features and thus more receptive to a traditional inverse design method, while the full grid still combines to produce the desired output. Each block is composed of a passive and reciprocal N-port network, where each component is a transfer function of variable order in Laplace domain. These blocks are combined in a grid, forming a cascaded S-parameter matrix which closely resembles the input. This method has the potential to reduce the total design space an inverse design algorithm has to search for, substantially speeding up computation
Heterogeneous catalytic materials for hydrothermal waste upgrading and remediation
No full textIncludes bibliographical references.2024 Summer.Purification of waste streams to reuse standards is a critical challenge in achieving economic circularity. To increase the feasibility of waste stream upgrading and remediation, the advantages of both homogenous and heterogeneous catalysts should be utilized. Further, the functionalities of solid heterogeneous catalysts in relevant reactions should be understood and taken as a foundation for optimization. This thesis applies heterogeneous catalysis under subcritical hydrothermal conditions to two areas relevant for sustainable waste stream management: (1) the upgrading of waste cooking oils to fuel grade hydrocarbons and (2) the destruction of per- and polyfluoroalkyl substances (PFAS) in water.
Awareness of the consequences and limits of fossil fuel usage has driven demand of alternative energy and fuel feedstocks. Waste cooking oils are high in fatty acid content, which through deoxygenation can be converted to long-chain hydrocarbons that can be used in drop-in fuel replacements for both diesel and sustainable aviation fuel. We review the functionality of nickel based non-noble metal catalysts supported on ZrO2 for the hydrothermal hydrogenation and decarboxylation of oleic acid, a fatty acid common in many waste cooking oils. Synthesis techniques and bimetal additives were compared and a monometal Ni/ZrO2 catalyst was found to be the most effective for hydrothermal deoxygenation of oleic acid. Kinetics studies (e.g., time, temperature, catalyst concentration, etc.) were completed to optimize reaction conditions. A variety of liquid hydrogen donor sources were screened (e.g., methanol, formic acid, glycerol) and methanol was found to yield optimal selectivity for heptadecane formation via catalytic decarboxylation. Initial fatty acid feedstock was also varied to assess the influence of molecular complexity on catalyst activity, and the degree of unsaturation was found to promote undesired side reactions and decrease selectivity for hydrocarbon production. Catalyst deactivation experiments identified sintering of the active Ni phase as a primary mode of deactivation.
A similar catalyst study was also applied for the remediation of PFAS-contaminated water. In 2024, a stringent federal drinking water standard limiting a variety of PFAS was established. Still, options for full destruction of PFAS remain limited, and understanding of how heterogeneous catalysts can facilitate their degradation remains relatively unexplored. Thus, noble metal and metal oxide catalysts were initially screened to identify catalysts for the degradation of perfluoroalkylsulfonic acids (PFSAs) under hydrothermal conditions. Noble metal catalysts (supported ruthenium and palladium) were identified to have the greatest potential for destruction of perfluorobutane sulfonate (PFBS). Further kinetics studies with ruthenium-on-carbon (Ru/C) (e.g., time, temperature, catalyst concentration, etc.) were then conducted to optimize catalyst performance. Considering the relative infancy of many PFAS detection methods, the analytical approach reviewed in this chapter also provides a useful didactic framework for identifying potential transformation byproducts. Through said intermediate identification, a novel degradation mechanism was proposed wherein reaction is initiated by cleavage of perfluoroalkyl C-C bonds. Although Ru/C mediated complete degradation of the parent PFSAs, only partial defluorination is observed and the remaining fluorine remains chemisorbed to the solid Ru/C following reaction, which is attributed to coupling of C-centered radicals (resulting from catalytic homolytic C-C bond cleavage) with the carbon support material. Application of hydrothermal alkaline treatment conditions liberated the chemisorbed F as fluoride ions.
Subsequently, prompted by activity differences seen in previous catalytic studies, we compared commercially purchased monoclinic ZrO2 against in house synthesized ZrO2 dominant in the tetragonal phase. Whereas monoclinic ZrO2 showed little reactivity with PFSAs, reaction with the tetragonal form of ZrO2 (t-ZrO2) was able to achieve >85% defluorination of PFSAs of varying chain lengths (e.g., TFMS, PFBS, PFOS). Degradation of perfluoroalkyl carboxylates was found to be slower than that of sulfonates, which was attributed to the formation of more nonpolar intermediate 1H-perfluoroalkanes by thermal decarboxylation at lower temperatures (e.g., 200 C), prior to the reactor reaching temperatures where the catalyst was active for PFAS destruction (e.g., 350 C). Catalyst activity was attributed to its density and strength distribution of basic sites, promoting hydrolytic PFAS degradation similar to the mechanism proposed for homogeneous hydrothermal alkaline treatment (HALT) of PFAS
Eyes on the Arctic: satellite monitoring of the Arctic LNG 2 terminal
No full textThe Arctic LNG 2 project operated by Novatek, Russia's largest independent natural gas producer, represents a significant undertaking in the global energy sector [1]. Situated on the Gydan Peninsula in the Arctic region, this ambitious project aims to tap into vast natural gas reserves and establish Russia as a leading exporter of LNG. The terminal is designed to eventually consist of three liquefaction trains, with a total planned annual production capacity of 19.8 million metric tons of LNG. This capacity is crucial for Russia's strategic goal of significantly increasing its share in the global LNG market, targeting a substantial portion of the expanding demand, particularly in Asia