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Journal Article
Published: 30 November 2019
The Canadian Mineralogist (2019) 57 (6): 867–883.
...Ingrid N. Kigai Abstract Practically all aspects of agate genesis generate debate. The time is ripe to clarify the most important enigmas concerning the environments of formation of agates and the related famous amethyst geodes of Brazil and Uruguay. Agates form over a wide range of temperatures...
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Journal Article
Published: 01 April 2012
The Canadian Mineralogist (2012) 50 (2): 325–340.
... in paragenesis with other Bi sulfosalts, chalcopyrite and hematite. Members of the pavonite homologous series are associated with bismuthinite derivatives and quartz of the amethyst variety. Three members of the cuprobismutite homologous series and four members of the pavonite homologous series have been found...
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Journal Article
Published: 19 July 2010
Geological Magazine (2010) 147 (6): 954–970.
...) and Artigas (Uruguay) were combined with flow-by-flow field studies of structures and scintillometric profiles to establish a consistent regional stratigraphic framework over at least 100 km. This greatly improves exploration capability for amethyst and agate geodes. A basalt, colada Mata Olho (Alegrete...
Journal Article
Journal: Elements
Published: 01 June 2009
Elements (2009) 5 (3): 159–162.
.... The intensity and shape of absorption bands in the OH region of the electromagnetic spectrum provide a test for synthetic amethyst. A band at 3595 cm -1 is present in the infrared spectrum of all natural amethysts but only rarely in synthetic ones. If present in synthetic amethyst, its full width at half...
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Journal Article
Published: 01 February 2008
The Canadian Mineralogist (2008) 46 (1): 111–124.
...Laura Baker Hebert; George R. Rossman Abstract Naturally occurring greenish quartz found within the context of amethyst-bearing deposits is not simply the result of the exposure of amethyst to thermal bleaching or exposure to the sun. Rather, it can represent a set of distinct color-varieties...
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Journal Article
Published: 08 August 2007
Canadian Journal of Earth Sciences (2007) 44 (8): 1041–1053.
... copper–nickel–PGE deposits (e.g., Seagull, Great Lakes Nickel). Silver-bearing veins occur in Paleoproterozoic Animikie Group sedimentary rocks in proximity to Midcontinent Rift-related mafic intrusions (e.g., Silver Islet, Silver Mountain). Lead–zinc–barite veins, uranium-bearing veins, and amethyst...
Journal Article
Published: 01 July 2007
Geological Magazine (2007) 144 (4): 731–739.
...DOMINIQUE PROUST; CLAUDE FONTAINE Abstract The amethyst geodes observed in the tholeiitic basaltic flow from the Triz quarry at Ametista do Sul (Rio Grande do Sul, Brazil) show particular wall-layering infillings with, from the outside inwards, celadonite, chalcedony, fine-grained quartz and large...
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Journal Article
Published: 01 January 2007
Geological Magazine (2007) 144 (1): 53–65.
...DOMINIQUE PROUST; CLAUDE FONTAINE Abstract Size distribution data obtained from detailed field study of bubbles and amethyst-geodes in the basaltic lava flows of the Serra Geral Formation (Ametista do Sul, Rio Grande do Sul, Brazil) are used in cooling and vesiculation models to infer the origin...
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Journal Article
Published: 01 March 2006
European Journal of Mineralogy (2006) 18 (2): 273–278.
...Masayuki KAWASAKI; Toshiro NAGASE; Kazuo ONUMA; Tooru KATSUMATA; Ichiro SUNAGAWA Abstract The surface microtopography of rough basal faces and internal inhomogeneities of amethyst crystals from Four Peaks, Arizona were investigated by means of optical, scanning electron microscopes...
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Journal Article
Published: 01 August 2001
Mineralogical Magazine (2001) 65 (4): 477–487.
...K. H. Yang; S. H. Yun; J. D. Lee Abstract The Eonyang amethyst deposit is thought to be spatially and temporally associated with the biotite granite of the Cretaceous Kyongsang Basin, South Korea. The euhedral quartz crystals in cavities in the aplite which intrudes biotite granite are colour-zoned...
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Journal Article
Published: 01 January 1994
Reviews in Mineralogy and Geochemistry (1994) 29 (1): 433–467.
Journal Article
Published: 01 September 1993
Canadian Journal of Earth Sciences (1993) 30 (9): 1955–1969.
...J. R. McArthur; E. A. Jennings; S. A. Kissin; R. L. Sherlock Abstract The Thunder Bay Amethyst Mine exploits a vein system in which the main zoned sequence consists of chalcedony, colorless quartz, and three to four stages of amethyst. The main sequence surrounds fragments of a brecciated earlier...
Journal Article
Published: 01 October 1986
American Mineralogist (1986) 71 (9-10): 1186–1193.
... enter the structure after a threshold of damage is reached and stabilize the metamict state by annealing local charge imbalance. Quartz crystals with both amethyst and citrine zones have molecular water in the citrine zones and dominantly hydroxide ion in the amethyst zones. This may be due...
Journal Article
Published: 01 December 1985
American Mineralogist (1985) 70 (11-12): 1180–1185.
... the trapped-hole centers on oxygens adjoining substitutional Al 3+ sites as they are formed thus preventing the appearance of smoky color. The resulting amethyst color is due to an absorption band related to the Fe 4+ produced. Since Fe 3+ only predominates over Fe 2+ in natural quartz formed under shallow...
Journal Article
Published: 01 August 1978
American Mineralogist (1978) 63 (7-8): 744–746.
...M. S. Joshi; P. N. Kotru; M. A. Ittyachen Abstract Triangular etch pits on rhombohedral surfaces due to hydrothermal etching are reported. Our experiments show that the hydrothermal etch pits on rhombohedral surfaces of amethyst have the same dislocation origin they have for quartz. We demonstrate...
Journal Article
Published: 01 April 1975
American Mineralogist (1975) 60 (3-4): 335–337.
... termed unlikely or not considered (and cited) at all. As a result the proposed models partly contradict these results (coordination and site occupation of Fe 3+ and Fe 2+ ) and partly do not (at least in our view) represent physically meaningful pictures (proposed structures of amethyst color centers...
Journal Article
Published: 01 August 1974
American Mineralogist (1974) 59 (7-8): 709–718.
...F. Hassan; Alvin J. Cohen Abstract Anisotropy of the characteristic absorption bands in a natural amethyst crystal from Brazil is demonstrated by the dependence of the value of the absorption coefficient upon the direction of the electric vector of incident light within the 4.13-0.95 eV region...
Journal Article
Published: 01 August 1974
American Mineralogist (1974) 59 (7-8): 719–728.
...Alvin J. Cohen; F. Hassan Abstract The generation and the removal of the various optical absorption bands in natural amethyst and in synthetic α-quartz doped with either Fe 2+ or Fe 3+ ions has been surveyed. Positive rhombohedral growth regions of synthetic α-quartz containing Fe 3+ ion proved...
Journal Article
Published: 01 April 1972
The Canadian Mineralogist (1972) 11 (2): 448–456.
Journal Article
Published: 01 July 1966
American Mineralogist (1966) 51 (7): 1088–1106.
...E. Wm. Heinrich; Joel R. Shappirio Abstract The Amethyst carbonatites in 12-Mile Park, Fremont County, Colorado are the northernmost representatives of the dike halo around the Iron Mountain-McClure Mountain alkalic complex. The deposits contain three main phases: 1) exomorphic zones of hematitized...