...T. Armbruster; B. Lazic; I. O. Galuskina; E. V. Galuskin; E. Gnos; K. M. Marzec; V. M. Gazeev Abstract The crystal structure of the rare skarn mineral trabzonite, Ca 4 [Si 3 O 9 (OH)]OH, from the type locality near Ikizdere, Turkey and from the Upper Chegem caldera, Northern Caucasus, Kabardino...

.... Fluorchegemite is associated with the high-temperature minerals larnite, edgrewite, wadalite, eltyubyuite, rondorfite, lakargiite, Th-rich kerimasite, and with their alteration products such as bultfonteinite, killalaite, hillebrandite, afwillite, trabzonite, and jennite. Fluorchegemite is colorless...

..., hydroxylellestadite and two mineral species first discovered in these skarns, defernite and trabzonite. Our data point to the possible existence of a fluorine-rich variant of rustumite and a hydroxyl-dominant variant of cuspidine. These minerals are associated with familiar skarn minerals. The temperatures achieved...

... occur sparingly in zones containing bultfonteinite, hillebrandite, jennite, and chegemite, as well as rare relics of larnite and rondorfite enclosed in a matrix of hydroxylellestadite. Edgrewite and hydroxyledgrewite are largely altered to jennite in places with admixed zeophyllite and trabzonite...

... and alternating Si 2 O 7 and SiO 4 units in dellaite. The similarity in cell dimensions and chemical composition suggests that trabzonite, Ca 4 Si 3 O 10 ·2H 2 O, with Si 3 O 10 trimers also belongs to the same family of structures. In addition to these scarce natural occurrences of dellaite, the synthetic...

...Fig. 1. Rusinovite spherulite in endoskarn: A, B – transmitted light, parallel nicols (a) and crossed nicols (b). (c) – BSE image, the frames indicate magnified fragments shown in Fig. 1d and e . (d) – replacement of rusinovite by trabzonite. Trabzonite has wadalite inclusions, which are altered...

.... Similar to the skarn at Kilchoan ( Agrell 1965 ) a high-temperature contact-metamorphic event is followed by hydrothermal alteration with an aqueous fluid at ca. 400 °C. Rustumite formed during the latter and is associated with epidote, tremolite, trabzonite, hillebrandite, tilleyte, killalaite, chlorite...

.... Lower-temperature associated minerals are: hillebrandite, afwillite, tobermorite, hibschite-katoite, hydrocalumite, ettringite-group minerals, trabzonite, and jennite. Rarely rusinovite replaces wollastonite. The mineral is white with a white streak, vitreous to silky, with a good cleavage on (010...

... with rondorfite crystals is noteworthy, whereas eltyubyuite, srebrodolskite and perovskite inclusions are enclosed in rondorfite ( Fig. 1f ). Bultfonteinite, hillebrandite, jennite, afwillite, zeophyllite, reinhardbraunsite, killalaite, trabzonite, grossular–katoite, hydrocalumite and minerals of the ettringite...