Contributions to mineralogy; No. VII

Genth, F. A.

doi:10.2475/ajs.s2-45.135.305

Cited by 5 publications

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“…The first detailed morphological account of calaverite was given by Penfield (1895) after the mineral had been first identified by Genth (1868). The latter author characterizes the (Au, Ag)Tez compound as a soft brittle substance without a well defined cleavage plane.…”

Section: Morphological Investigations On Calaveritementioning

confidence: 99%

The morphology of calaverite (AuTe2) from data of 1931. Solution of an old problem of rational indices

Janner¹,

Dam²

1989

Acta Cryst Sect A

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The anomalous high-index faces (hkl) of the mineral calaverite (Au~_xAgxTe2) measured goniometrically in the year 1931 by Goldschmidt, Palache & Peacock [Neues Jahrb. Mineral (1931), 63, 1-58] are re-interpreted and related to the wave vector q of the displacive incommensurate modulation which was recently found in the crystal structure. All crystal * Present address: Philips Research Laboratories, PO Box 80.000, NL-5600 JA Eindhoven, The Netherlands.faces (including the high-index ones) can be given four low indices (hklm), using q as a fourth basis vector. From this an almost hundred-year-old anomaly in crystal morphology is in principle solved. I. IntroductionThe present investigation started from a non-applicability of the law of rational indices to crystal growth forms of calaverite Aul_pAgpTe2 (p < 0.15) (Smith, 1902;Goldschmidt, Palache & Peacock, 1931).Classically (Bravais-Friedel) the morphology of crystals is related to the existence of a crystal lattice. This crystal lattice is even implicitly suggested by Haiiy's law of rational indices. The latter can be extended to the use of four or more rational indices in order to describe the crystal forms of modulated crystals (Janner, Rasing, Bennema & van der Linden, 1980;Dam & Janner, 1983, 1986. The fact that the number of indices can be larger than three reflects the fact that the number of fundamental periodicities can also be larger than three, which is a key concept for the understanding of crystal faces. Hence, in the description of crystal morphology one is not necessarily restricted to the three periodicities generating a three-dimensional space lattice. In the onedimensional modulated case the modulation wave vector q = aa* + fib* + yc* has to be added as a fourth basic vector to the three ones of the undistorted reciprocal-lattice unit cell: a*, b*, c*. Any crystal face of a one-dimensionally modulated crystal is then labeled by the four indices (hklm) of the corresponding face normal given by k--ha*+kb*+lc*+ mq.The use of four indices is closely related to the superspace approach as introduced for incommensurately modulated crystals by de Wolff (1977) and Janner & Janssen (1977. Indeed, the presence of fundamental periodicities in a given crystal does not mean that the structure is periodic in space. One can eventually restore the familiar lattice periodicity by embedding the crystal in a larger space, the superspace, with as many dimensions as there are fundamental periodicities. In Dam & Janner (1986) the details of this approach are explained and applied to the morphology of the modulated phases of the crystal tetramethylammonium tetrachlorozincate [(CH3)aN]2ZnCI 4. The most recent experimental result of morphological research on that compound is the observation of a roughening of a satellite orientation (hklm) upon a change of the modulation wave vector q as a function of temperature (Dam, 1985). Note that superspace embedding is necessary for a symmetry characterization in terms of Euclidean space groups, but not if that is not req...

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Section: Morphological Investigations On Calaveritementioning

confidence: 99%

The morphology of calaverite (AuTe2) from data of 1931. Solution of an old problem of rational indices

Janner¹,

Dam²

1989

Acta Cryst Sect A

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“…(HS: II, viii). Characterized as "calaverite" [Genth, 1868, Hillebrand, 1895, this gold telluride AuTe 2 is an ore found in different parts of the world, including Australia, USA, China and Russia [Carnot, 1901, Lenher, 1902, Zhang and Mao, 1995, Vikent'eva et al, 2020. Naturally, it is mostly used as a resource for gold, e.g.…”

Section: Le Volcan D'or: a Volcano That Spits Out Gold Novelist's Inv...mentioning

confidence: 99%

Literature & Geosciences: Jules Verne’s geological novels, from the 19th to the 21st century

Bollinger¹

2022

Comptes Rendus. Géoscience

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A friend of both François Arago, who founded the Comptes Rendus de l'Académie des Sciences, and his brother Jacques, a renowned traveler, Jules Verne wrote many novels in which his heroes made use of the most recent scientific knowledge of the time. While the novelist only really had a legal background, he did keep himself apprised of all the latest scientific developments. This study, based on a selection of novels wherein geology is very present as well as on contemporary or current scientific publications, shows that today's understanding of the geosciences does indeed agree with Jules Verne's extrapolations. Among the subjects developed are: coal extraction and the hazards of firedamp, so-called "mud volcanoes" and the special case of gold trickling from volcanoes, diamond geo-genesis, the creation of an inland sea in the Sahara, and a foretelling of the Anthropocene Epoch.Résumé. Ami de François Arago, le fondateur des Comptes Rendus de l'Académie des Sciences, et de son frère Jacques, un grand voyageur, Jules Verne (1828-1905) a écrit de nombreux romans dans lesquels ses héros utilisent les connaissances scientifiques les plus récentes de l'époque. En effet le romancier, s'il n'avait qu'une formation juridique, se tenait informé des développements de la science. Dans cette étude, basée d'une part sur un choix de romans où la géologie est très présente, et d'autre part sur des publications scientifiques contemporaines ou actuelles, on montre que les géosciences d'aujourd'hui sont en accord avec les extrapolations de Jules Verne. Parmi les sujets développés, citons : l'extraction du charbon et les risques de grisou, les volcans dits « de boue » et le cas particulier de l'or qui s'écoule de certains volcans, la géo-genèse des diamants, la création d'une mer intérieure dans le Sahara, et une prédiction de l'époque Anthropocène.

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“…Calaverite is a gold tellurium mineral containing a few percents of Silver (up to 3% Ag) identified in 1868 by Genth [101] in the Stanislau mine, Calaveras (California). In 1895 Hillebrand examined calaverite crystals from the Cripple Creek mine in Colorado, characterized by a very small silver content [102].…”

Section: Morphology Of Calaverite Autementioning

confidence: 99%

From crystal morphology to molecular and scale crystallography

Janner

Janssen

2015

Phys. Scr.

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A number of topics, ranging from morphology of aperiodic crystals to indexed enclosing forms of axial-symmetric proteins, nucleic acids and viruses, have been selected among those investigated by the authors in 50 years of research. The basic symmetries involved in fields like superspace, molecular and scale crystallography, are considered from a personal point of view in their time evolution. A number of specific subjects follow, chosen among a few highlights and presented according to the experience of the authors: snow crystals, calaverite , the incommensurately modulated crystals , and the mitochondrial ferritin.

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Contributions to mineralogy; No. VII

Abstract: * In Dana's System of Mineralogy, ii, 64, it is mentioned that minute crystals, which I had observed to occur with gold ores at Gold Hill, Rowan Co., N. C., were probably sylvanite j subsequent examina.tion, however, proved them to be bismuthine.

Cited by 5 publications

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The morphology of calaverite (AuTe2) from data of 1931. Solution of an old problem of rational indices

The morphology of calaverite (AuTe2) from data of 1931. Solution of an old problem of rational indices

Literature & Geosciences: Jules Verne’s geological novels, from the 19th to the 21st century

From crystal morphology to molecular and scale crystallography

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