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Topas
LiteraturVeröffentlichungen
Topas Literatur.
Frei verfügbare Veröffentlichungen mit weiteren Informationen über den Topas (Vorkommen, Eigenschaften, Farbursachen . . .)
IOP Conference Series: Materials Science and Engineering, Vol. 49 (2013), pp. 1-4
Abstract. The results of investigation of infrared, Raman and UV-Visible absorption spectra of natural topaz crystals from Ukraine before and after fast neutron irradiation are presented. We assume that the ~ 620 nm band in topaz crystals is associated with the presence of Cr3+ and Mn2+ impurities.
Tasmanian Geological Survey, Record 2012/01, pp. 4-10
Abstract. Colourless to pale-coloured gem topaz crystals, locally known as ‘Killiecrankie diamonds’, have been recovered in some abundance from Killiecrankie Bay, Flinders Island, since at least 1803, and are probably some of the earliest gems recorded and exported from Australia. The crystals derive from weathering of pegmatitic pockets within granite, but most are recovered from alluvial deposits, some offshore. Similar topaz occurs on other parts of the island, and on Cape Barren Island.
Vestnik Otdelenia nauk o Zemle RAN, Vol. 4 (2012)
Abstract. For the first time the Cr-containing topaz single crystals with unusual alexandrite effect and intensive fluorescence under influence of ultra-violet light are grown up. Growth conditions and the external and internal morphology of crystals and their physical properties is studied.
extraLapis No. 14: Topaz - Perfect Cleavage (2011), pp. 88-93
Abstract. Petrologists study inclusions in topaz to understand topazforming processes in natural environments. They are interested in the type and composition of the media, such as magmas, hydrothermal solutions, supercritical fluids, or vapors, from which the topaz crystallized.
American Mineralogist, Vol. 91 (2006), No. 11-12, pp. 1839-1846
Abstract. The crystal chemistry of a natural topaz [with OH/(OH + F) < 0.5] was reinvestigated by means of laser ablation inductively coupled plasma mass spectroscopy, single-crystal X-ray diffraction (at 298 K) and neutron diffraction (at 298 and 10 K), and polarized infrared spectroscopy to define unambiguously the real symmetry of topaz, the location of the proton and its thermal displacement parameters at room and low temperatures, the hydrogen-bonding and the vibration modes (stretching and bending) of the OH dipole. X-ray and neutron structural refinements allow us to infer that the crystal structure of natural topaz with OH/(OH + F) < 0.5 can be described with the Pbnm space group.
Gems & Gemology, Winter, Vol. 32 (1996),No. 4, pp. 232-241
Abstract. The Capao mine is one of the oldest and most productive fully mechanized Imperial topaz mines in the historic Ouro Preto area of Minas Gerais, Brazil. Bulldozers, water cannons, and dragscrapers are used in two main pits to remove the thick brown over-burden for processing to recover topaz crystals in a broad range of sizes and colors. The rarest color is pinkish purple to purple. Heat treatment will turn some brownish yellow or orange Imperial topaz to "peach" or pink. Preliminary testing suggests that there may be a difference in fluorescence between heat-treated and non-heat-treated topaz.
Physica Status Solidi A, Vol. 29 (1994), No.2, pp. 659-663
Abstract. Trace element distributions in topaz [Al2SiO4(F,OH)2] single crystals display both sectoral and intrasectoral zoning of trace elements as a function of growth-surface structure. Differential interference contrast microscopy shows that the dominant {110} form exhibits large, polygonized, spiral gowth hillocks with four vicinal faces, each comprising an array of parallel growth steps. Cathodoluminescence microscopy and synchrotron X-ray fluorescence microanalysis show that during gowth trace elements (As, Fe, and Ti) were differentially incorporated into vicinal faces having symmetrically nonequivalent step orientations, producing intrasectoral zoning in the bulk crystal. Subsectors that formed from vicinal faces related by surface symmetry possess identical compositions. In all cases, there is precise correlation between surface microtopography and trace element distribution, demonstrating a surface-structural control of trace element incorporation.
physica status solidi (a), Vol.133 (1992), No. 2, pp. 473–479
Abstract. Natural crystals of topaz [Al(OH, F)]2SiO4, from three localities (yellow from Brazil, pink from Africa, and blue from unknown locality) are studied at RT by using the IR technique. Infrared signals arising from stretching and bending modes of OH−ions, SiO4, tetrahedra, and AI(OH, F)O4 octahedra are detected. Some peaks which according to theoretical considerations are expected to attain first-order activity, are not observed in this study either because of their low intensity or/and that they are overlapped by stronger bands.
Bulletin of the Geological Society of Finland, Vol. 63 (1991), pp. 25-40
Abstract. The Ahvenisto rapakivi complex is a satellite northwest of the large Wiborg rapakivi batholith in Southeastern Finland. The rapakivi rocks are surrounded by rapakivi-age gabbros, anorthosites, monzodiorites and diabases. The complex consists of a highly evolved suite of several texturally, mineralogically and geochemically different rapakivi types. They are anorogenic and their age is 1640-1630 Ma. The youngest phases of the rapakivi suite are even-grained, topaz-bearing and geochemically specialized tin granites. They also show the characteristics of A-type granites. Earlier known rapakivi granites in Finland of the same type have been described from Eurajoki and Kymi.
Gems & Gemology, Fall, Vol. 25 (1989), No. 3, pp. 165-167
Abstract. Faceted colorless topaz containing acicular inclusions has been offered for sale as "rutilated" topaz. Earlier investigations have shown the inclusions to be limonite-stained etched dislocation channels. This article reports on the use of heat treatment to alter the limonite staining to hematite, thus changing the color of the inclusions and making them more prominent.
Gems & Gemology, Fall , Vol. 22 (1986), No. 3, pp. 140-151
Abstract. In addition to the relatively recent discovery of significant amounts of emerald, aquamarine, and ruby, Pakistan has also begun to produce fine gem-quality pink topaz. In a small hillock of recrystallized limestone north of Katlang, narrow calcite veins encase pink topaz crystals up to 3 cm long accompanied by larger amounts of reddish brown, tan, and colorless topaz crystals. More than 70,000 ct of gem-quality pink topaz has been reported to date. The refractive indices, optic axial angle, unit-cell dimensions, and density of the topaz are influenced by a partial replacement of fluorine by hydroxyl ions. The color is due to trace elements –principally chromium (Cr3+). Treatment experiments revealed that the color of the brown, tan, and colorless topaz from this source may be improved by irradiation and heat.
American Mineralogist, Vol. 69 (1984), pp. 223-236
Abstract. Two sequences of rhyolite lava flows and associated pyroclastic deposits are exposed in the Thomas Range (6 m.y.) and at Spor Mountain (21 m.y.) in west-central Utah. Both contain topaz indicative of their F-enrichment (>0.2%) and aluminous nature. The rhyolites are part of the bimodal sequence of basalt and rhyolite typical of the region. Moderate changes in major elements coupled with large variations in trace elements in vitrophyres from the Thomas Range are generally consistent with fractionation of observed phenocrysts. Especially important roles for the trace minerals are suggested.
Gems & Gemology, Vol. 19 (1983), No. 1, pp. 12-20
Abstract. For over 200 years, the only known source of imperial topaz has been a small mining district near Ouro Preto. One of the oldest and most productive mines in the district is the Capao do Lana. This article examines the history of the Ouro Preto district as well as the geology of the area and occurrence of the topaz. Special attention is focused on the relatively sophisticated recovery methods used at the Capao do Lana mine. Also discussed is the gemology of this most prized color variety of topaz.
Mineralogical Magazine, Vol. 43 (1979), pp. 237-241
Abstract. A study has been made of topaz crystals showing a sectoral texture related to the growth of the crystal, and showing anomalous optical properties within the sectors. The growth surfaces responsible for the development of most of the sectors have been identified. The fluorine/hydroxyl sites in topaz are symmetrically equivalent in the solid crystal, but at a growth surface this equivalence may be lost, resulting in a reduction in the crystal symmetry and the ordering of fluorine and hydroxyl, the ordering scheme being retained once the crystal has formed. The reduction in symmetry expected to be produced by this ordering is in general agreement with the actual reduction in symmetry indicated by the optical properties. Heating of the topaz to about 950 ~ results in the almost complete disappearance of the optical anomalies due to disordering, which may be related to the loss of hydroxyl from the crystal. Anomalous pyro- and piezoelectric phenomena may also be the result of ordering. Published optical and X-ray determinative curves for fluorine in topaz may give erroneous results for ordered topaz.
Mineralogical Magazine, Vol. 43 (1979), pp. 175-6
Abstract. Colorless, purple, and pink topaz and transparent quartz crystals have been found in calcite veins (with or without milky quartz) in calcareous rocks near Katlang (34 ~ 24' N, 72 ~ 6' E), Mardan district. The veins do not contain any fluorite nor the country rocks any topaz. The topaz and transparent quartz crystals are mostly broken and perfectly euhedral outlines are very rare. Refractive indices, 2V, specific gravity, and the fluorine (determined) and H20 + (calculated) contents of two topaz crystals are suggestive of their high I00 OH/(OH+F) ratios (> 25). Rather than being derived, the topaz may have formed in situ by hydrothermal/pneumatolytic activity, followed by tectonic movements that fractured the crystals and resulted in their incorporation in later-formed vein calcite.
Journal Mineralogical Society of America, Vol. 20 (1979), No. 5, pp. 354-363
Abstract. Renewed operations in the pegmatites of Devil's Head, in the Pike's Peak region, have yielded a suite of noteworthy crystals of topaz associated with quartz, microcline, albite, fluorite and cassiterite. The collection includes some topaz crystals of outstanding size and regular development and many smaller crystals of unusually distorted habits.
American Mineralogist, Vol. 56 (1971), pp. 24-30
Abstract. The crystal structure of topaz (Pbnm, a=4.6499; b=8.7968; c=8.3909 Å) is described using positional parameters determined by Ladell (1965). It is based on monolayers of oxygen alternating with layers of composition F2O1 in the close-packed sequence ABAC. The key structural unit is a crankshaft chain of edge-sharing AlO4F2 octahedra and corner-sharing SiO2 tetrahedra running parallel to z. This explains the [001] prismatic habit of topaz and the fact that it is optically positive. The perfect {001} cleavage is parallel to the only planes which can be passed through the structure without breaking Si-O bonds. The thermal expansion is greatest perpendicular to the cleavage which is consistent with the fact that {001} represents the plane of the weakest bonds. The mean Si-O bond length is 1.641 Å, ~0.02 Å longer than that expected for a three-coordinated oxygen. The mean Al-F and AI-O bonds are 1.795 and 1 895 Å, respectively.
Mineralogical Magazine, Vol. 17 (1913), No. 78, pp. 39-45
Abstract. It is only recently that the mineral topaz has been found in any considerable quantity in Canada. Previous to the discovery of the topaz of York County, New Brunswick, in 1911, it was distinctly a rarity among Canadian minerals and had never been found crystallized in any Canadian locality. The above-mentioned district, however, has yielded both the massive and crystallized varieties in fair abundance and some fairly perfect crystals have been obtained for measurement. The first topaz reported from Canada appears to have been of somewhat doubtful authenticity. It is stated that : ' At the London Exhibition, 1862, Mr. McDonald exhibited two topazes (?) from Cape Breton, one in the rough, and the other, which had been cut at Pictou, half an inch in length and of a yellow colour, the variety peculiar to Brazil, which leads to the inference that these stones may have been citrine or artificially decolorized smoky quartz, and not the true mineralogical topaz.'.