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Optical Properties of Solids
Published in Elaine A. Moore, Lesley E. Smart, Solid State Chemistry, 2020
Elaine A. Moore, Lesley E. Smart
Another interesting natural example of color centres lies in the color of smoky quartz and amethyst. These semiprecious stones are basically crystals of silica (SiO2) with some impurity present. In the case of smoky quartz, the silica contains a little aluminum impurity. The Al3+ substitutes for the Si4+ in the lattice and the electrical neutrality is maintained by H+ present in the same amount as Al3+. The color centre arises when ionising radiation interacts with an [A1O4]5− group, liberating an electron that is then trapped by H+: [AlO4]5−+H+=[AlO4]4−+H.
The Breznik epithermal Au occurrence, Western Srednogorie - Bulgaria: an “atypical” (?) low-sulphidation hydrothermal system
Published in Adam Piestrzyński, Mineral Deposits at the Beginning of the 21st Century, 2001
J. Crummy, I. Mutafchiev, I. Velinov, R. Petrunov
Generally, dominating pyrite and scarce galena, sphalerite, chalcopyrite, tetrahedrite, tennantite, bournonite, Co-Ni-Fe-S phases, arsenopyrite, marcasite and argentite occur within the mineralised areas. Gangue minerals are abundant Mg-, Fe- and Mn- carbonates and some quartz (including amethyst and chalcedony). Gold occurs mainly in Mn carbonate and there is no direct geochemical correlation with Pb, Zn and Cu. The textures are chiefly vein-disseminated, and also identifiable are breccia (comprising quartz and carbonate) textures. The potentially most of economic intervals have a width of 2 – 20m. These intervals do not show clear contacts and their boundaries at depth can be determined on the basis of the geochemical analysis. Their length varies from some tens to 250 meters and they were traced by drillings down to about 100 meters depth.
Inorganic Polymers
Published in Charles E. Carraher, Carraher's Polymer Chemistry, 2017
Quartz is found in several forms in all three major kinds of rocks—igneous, metamorphic, and sedimentary. It is one of the hardest minerals known. Geologists often divide quartz into two main groupings—course crystalline and cryptocrystalline quartz. Course crystalline quartz include six-sided quartz crystals and massive granular clumps. Some colored varieties of coarse crystalline quartz crystals, amethyst and citrine, are cut into gemstones. Others include pink (rose), purple, and milky quartz, but most coarse crystalline quartz is colorless and transparent. Sandstone is a ready example of granular quartz. Color is a result of the presence of small amounts of metal cations such as calcium, iron, magnesium, and aluminum.
Basaltic dykes and their xenoliths from the Gerroa–Kiama region, southern Sydney Basin, New South Wales: evidence for multiple intrusive episodes
Published in Australian Journal of Earth Sciences, 2022
S. Abu-Shamma, I. T. Graham, P. Lennox, G. Bann, A. Greig
In hand-specimen, most of the latites, which are shoshonitic basalts (Berkeley, Minnamurra, Dapto, Saddleback and Blowhole latite members), are porphyritic with a holocrystalline groundmass and vary in colour from grey to light grey or even black (Carr, 1984). Phenocrysts consist of plagioclase, clinopyroxene, titanomagnetite and chlorite pseudomorphs after olivine. The most common phenocryst is plagioclase, and, in some samples, this is the only phenocrystic phase. The groundmass of the shoshonitic basalts consists mainly of clinopyroxene, feldspar and titanomagnetite and have intergranular, orthophyric or pilotaxitic textures. Segments of the shoshonitic basalts exhibit vesicles or amygdales, with the amygdales containing hematite, quartz (including amethyst), chlorite, chalcedony, prehnite, pumpellyite, laumontite and epidote.
Abstracts from the 2017–2018 Mineral Deposits Studies Group meeting
Published in Applied Earth Science, 2018
L. Santoro, St. Tshipeng Yav, E. Pirard, A. Kaniki, G. Arfè, N. Mondillo, M. Boni, M. Joachimski, G. Balassone, A. Mormone, A. Cauceglia, N. Mondillo, G. Balassone, M. Boni, W. Robb, T. L. Smith, David Currie, Finlay Stuart, John Faithfull, Adrian Boyce, N. Mondillo, C. Chelle-Michou, M. Boni, S. Cretella, G. Scognamiglio, M. Tarallo, G. Arfè, F. Putzolu, M. Boni, N. Mondillo, F. Pirajno, N. Mondillo, C. Chelle-Michou, M. Boni, S. Cretella, G. Scognamiglio, M. Tarallo, G. Arfè, Saltanat Aitbaeva, Marina Mizernaya, Boris Dyachkov, Andrew J Martin, Iain McDonald, Christopher J MacLeod, Katie McFall, Hazel M Prichard, Gawen R T Jenkin, B. Kennedy, I. McDonald, D. Tanner, L. Longridge, A. M. Borst, A. A. Finch, H. Friis, N. J. Horsburgh, P. N. Gamaletsos, J. Goettlicher, R. Steininger, K. Geraki, Jonathan Cloutier, Stephen J. Piercey, Connor Allen, Craig Storey, James Darling, Stephanie Lasalle, A. Dobrzanski, L. Kirstein, R. Walcott, I. Butler, B. Ngwenya, Andrew Dobrzanski, Simon Howard, Lore Troalen, Peter Davidson, Rachel Walcott, Drew Drummond, Jonathan Cloutier, Drew Drummond, Adrian Boyce, Robert Blakeman, John Ashton, Eva Marquis, Kathryn Goodenough, Guillaume Estrade, Martin Smith, E. Zygouri, S. P. Kilias, T. Zack, I. Pitcairn, E. Chi Fru, P. Nomikou, A. Argyraki, M. Ivarsson, Adrian A. Finch, Anouk M. Borst, William Hutchison, Nicola J. Horsburgh, Tom Andersen, Siri Simonsen, Hamidullah Waizy, Norman Moles, Martin Smith, Steven P. Hollis, Julian F. Menuge, Aileen L. Doran, Paul Dennis, Brett Davidheiser-Kroll, Alina Marca, Jamie Wilkinson, Adrian Boyce, John Güven, Steven P. Hollis, Julian F. Menuge, Aileen L. Doran, Stephen J. Piercey, Mark R. Cooper, J. Stephen Daly, Oakley Turner, Brian McConnell, Hannah S. R. Hughes, Hannah S. R. Hughes, Magdalena M. Matusiak-Małek, Iain McDonald, Ben Williamson, James Williams, Guy Dishaw, Harri Rees, Roger Key, Simon Bate, Andy Moore, Katie McFall, Iain McDonald, Dominque Tanner, Manuel Keith, Karsten M. Haase, Daniel J. Smith, Reiner Klemd, Ulrich Schwarz-Schampera, Wolfgang Bach, Sam J Walding, Gawen RT Jenkin, Daniel James, David Clark, Lisa Hart-Madigan, Robin Armstrong, Jamie Wilkinson, Gawen RT Jenkin, Hugh Graham, Daniel J Smith, Andrew P Abbott, David A Holwell, Eva Zygouri, Robert C Harris, Christopher J Stanley, Hannah L.J. Grant, Mark D. Hannington, Sven Petersen, Matthias Frische, Fei Zhang, Ben J. Williamson, Hannah Hughes, Joshua Smiles, Manuel Keith, Daniel J. Smith, Chetan Nathwani, Robert Sievwright, Jamie Wilkinson, Matthew Loader, Daryl E. Blanks, David A. Holwell, W.D. Smith, J.R. Darling, D.S. Bullen, R.C. Scrivener, Aileen L. Doran, Steven P. Hollis, Julian F. Menuge, John Güven, Adrian J. Boyce, Oakley Turner, Sam Broom-Fendley, Aoife E Brady, Karen Hudson-Edwards, Oakley Turner, Steve Hollis, Sean McClenaghan, Aileen Doran, John Güven, Emily K. Fallon, Richard Brooker, Thomas Scott
Other localities with Zr, Nb, Ti, Th, and HREE mineralisation include Bear Lodge, Amethyst, Wet Mountains, Iron Hill, Magnet Cove (USA), Goudini, Salpeterkop (South Africa), and Gross Brukkaros (Namibia) (Andersen et al. 2016; Staatz 1983; Verwoerd et al. 1995; Armbrustmacher 1980; Flohr 1994; Werner and Cook 2001), although the degree of exploration at each locality is highly variable. Commonalities include features of shallow emplacement, such as emplacement through extrusive rocks or breccia pipes, as well as extensive host rock alteration and silicification, similar to the process of fenitisation. In combination, these features are circumstantial evidence for formation from a late hydrothermal fluid in a shallow, subvolcanic system, and may be analogous with epithermal mineralisation.