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Minerals
Published in Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough, Earth Materials, 2019
Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough
Some minerals may conduct electricity. Electrical conduction occurs when a mineral’s electrons can move throughout its structure. Such will be the case in structures containing metallic bonds. The native metals, such as copper, are the best examples. Small amounts of electrical conduction may also occur in minerals with defects and other imperfections in their structures. Other minerals, while being unable to conduct electricity, may hold static charges for brief times. They may be charged by exposure to a strong electric field, a change in temperature, or an application of pressure. A mineral charged by temperature change is pyroelectric; a mineral charged by pressure change is piezoelectric. Because they are difficult to measure, electrical properties are not often used for mineral identification.
The native metals
Published in R. F. Tylecote, The Prehistory of Metallurgy in the British Isles, 2017
For the purpose of this study the term native is applied to metals that are found in the metallic state and which are not produced from ores by smelting. Gold, and some copper occur in this form, and meteoric iron is also in this sense a native metal. These three metals were once lying on the earth’s crust waiting for man to make use of them. Silver also occurs in native form, but is thought to have existed in such a manner only in deep veins, and was therefore not available to early man.1 Apart from these, the only other native metal of use to early man was arsenic.
Lifetime prediction of bonded structural patch repairs for wind turbine pitch bearing strengthening
Published in The Journal of Adhesion, 2022
J. Manterola, I. Leciñana, J. Zurbitu, H. Zabala, I. Urresti, M. Olave
The epoxy-based structural adhesive Scotch Weld EC-9323-2 B/A by 3 M was used.[17] This two-part adhesive was handled at room temperature and cured at 80°C for 3 h before testing. To determine the Young modulus and yield stress of the adhesive, three dumbbell specimens were manufactured using a Teflon mould having the specific geometry. Later, specimens were cured, and tested following ASTM D638[18]. An extensometer was coupled to determine the Poisson’s ratio. A digital image correlation (DIC) technique was also applied to obtain an accurate value.[19] Three SLJ specimens were manufactured and tested following ASTM D1002[20] to determine the ultimate shear stress of the adhesive. High-strength aluminium alloy type Al 7075-T6 with a yield strength of 550 MPa was used to prevent any plastic deformation during the test. Aluminium substrates were first rough filed and then cleaned with acetone to remove native metal oxide. Prior to bonding, the substrates were cleaned again with isopropyl alcohol to improve adhesion. (Figure 2)
A review of the current state of knowledge on gold mineralisation in Benin Republic, West Africa
Published in Applied Earth Science, 2019
Fatchessin Bruno Adjo, Anthony Temidayo Bolarinwa, Luc Adissin Glodji, Franck Wilfried Nguimatsia Dongmo, Jerry Olugbenga Olajide-Kayode
Quartz-sulphide veins are exemplified by the Perma and Pessoulou deposits. In these deposits, gold exhibits three forms: free native metal, tellurides and combined or included in sulphides. Gold of the Perma deposit is often associated with pyrite (FeS2), chalcopyrite (CuFeS2), galena (PbS), sphalerite (ZnS), covellite (CuS), silverite (Ag2S) and tetrahedrite ((Cu,Fe)12Sb4S13)); oxide such as magnetite (Fe3O4), hematite (Fe2O3), rutile (TiO2), azurite (Cu3CO3(OH)2); and gangue minerals such as quartz, muscovite, chlorite and carbonate (Kirov et al. 1976; Kirov et al. 1981; Depciuch and Azonsi 1983; Kirov and Boboé 1983; Yessoufou 1991). The sulphide content is usually low (less than 5%) and pyrite is by far the most common sulphide. In the Pessoulou area, gold is associated with lead, silver and copper mineralisation. Within both deposits, muscovite, carbonate and chlorite occur in the vein alteration halos in the locations. However, the chemical composition of these minerals, as well as that of native minerals, varies with respect to host-rock lithology.
Producing a thin coloured film on stainless steels – a review. Part 2: non-electrochemical and laser processes
Published in Transactions of the IMF, 2023
G. T. Alliott, R. L. Higginson, G. D. Wilcox
Labanowski and Glowacka,20 who observed thermal tinting on stainless steel welds, postulate that the properties of the oxide are determined by five factors: Time and temperature of heat exposureComposition of the atmosphere during the heating and cooling processChemical composition of the basic alloySurface physical conditionBinding of the oxide to the native metal