Тип публикации: статья из журнала
Год издания: 2022
Идентификатор DOI: 10.17223/25421379/23/6
Ключевые слова: ammolite, gem stone, iridescent nacre, krasnoyarsk krai, pearlanorisk, turonian stage
Аннотация: In 2017, ammonites showing a colorful iridescent nacreous surface began to appear on the Russian market. The deposit is located near Norilsk in the Taymyr Municipal District, Krasnoyarsk Krai, northwestern Siberia. Geographically, the site is located at the junction of the northwestern part of the Kharayelakh mountains and the westПоказать полностьюern ending of the North-Siberian lowlands, in the field of sedimentary deposits of the Yenisei-Khatanga trough, in the lower reaches of the Ikon, Kumga and Talmi Rivers — the right tributaries of the Pyasina River. The ammonites Placenticeras sp. nov. up to 1.2 m across are encased in calcareous sandstone concretions associated with Late Cretaceous (Turonian) sedimentary deposits. Gigantic ammonite shells have white and black nacre, with weak iridescence of a part of them. Iridescence of the fossilized nacreous surface has been enhanced by impregnation in vacuum with epoxy resin and is associated with preserved platy aragonite layers of the ammonite walls. It is assumed that the intervals between aragonite layers and micropores in original shells were filled by organic material — conchiolin, which was later destroyed as a result of lithification. When these cavities are filled with colorless epoxy resin, the optical properties of the nacre — translucence and iridescence are restored. The study of the fossilized nacre showed that the aragonite microcrystals are 10–15 µm long and 0.4–1.5 µm thick. The nacreous layer consists of (wt. %): aragonite – 93, calcite – 1.5, apatite – 2.5, faterite – 2, and siderite – 1; traces of pyrite and quartz are present. The observed iridescence colors of ammolite – red, yellow, green, blue and violet – are determined by the thickness of aragonite layers and intervals between them, as well as the difference in the size and shape of micropores in the nacre. The iridescence color varies when the angle of view changes. The iridizing fossil nacre from the north of the Krasnoyarsk Krai is a high-quality jewelry material in terms of its decorative and technological properties. Moreover, it can be used to manufacture a wide range of souvenir items, jewelry ornaments, collection items, interior items and a highly decorative facing stone. The Norilsk ammolite samples are of significant collection interest. Items made of whole shells are unique. This is evidenced by the result of a giant ammonite shell refinement. The largest shell is called "Emperor of Taimyr" and is 62×46×15 cm in size. In terms of its quality and sizes, the Norilsk ammolite is comparable with the best examples of ammolites from the known Medvezhya lapa deposit in the south of the Alberta Province (Canada) and beats all currently known occurrences of similar resources in the Ulyanovsk and Yaroslavl Regions, which makes it unique for the Russian Federation. © 2022, Faculty of Geology and Geography, Tomsk State University. All rights reserved.
Журнал: Geosfernye Issledovaniya
Выпуск журнала: Vol. 2022, Is. 2
Номера страниц: 101-111
ISSN журнала: 25421379
Издатель: Faculty of Geology and Geography, Tomsk State University