Detailed information



The world market enjoys an expansive range of the interior- and jewelry-quality ammonite extracted at the Modiroval deposit in Madagascar. Mining is carried out through pit-holes, with primitive tools and without preliminary exploration. The productive stratum occurs at a depth down to 20 m and belongs to the Albian stage. It is traced as a strip of 500 m for the space of 15 km. The productive stratum is dense marl composed of calcite, siderite and aragonite. Small quantities of apatite, kaolinite, quartz, goethite, chlorite, hydromica and pyrite are present. Out of accessory minerals, ilmenite, zircon and organic matter are identified. Marl is rich with fine mineralized pockets 0.05–1.5 mm in size. The fossil shells preserve mostly initial aragonite composition. Formation of the productive stratum is connected with the massive mortality of fossil shells and their concentration deep under the sea. Mineralization of fossil shells during diagenesis of marine sediments took place under low temperatures and high content of iron. Madagascar experience of ammonite extraction and processing can be of use in Russia which holds considerable reserves of this jewelry- and ornamental-quality material with the unique decorative and process characteristics.

: 7
УДК: 622.793.5
DOI: 10.25018/0236-1493-2018-7-0-160-168
Authors: Petrochenkov D. A.

Authors' Information:
Petrochenkov D.A., Candidate of Geological and Mineralogical Sciences,
Assistant Professor, e-mail: p-d-a@mail.ru,
Russian State Geological Prospecting University named after Sergo Ordzhonikidzе
(MGRI-RSGPU), 117997, Moscow, Russia.

Key words:
Jewelry- and ornamental-quality raw material, ammonite, nautilus, Cretaceous deposits, marl, aragonite, Madagascar.


1. Bukanov V. V. Tsvetnye kamni i kollektsionnye mineraly [Цветные камни и коллекционные минералы], Saint-Petersburg, 2014, 416 p.

2. Petrochenkov D. A. Kamnesamotsvetnoe syr'e Ul'yanovskoy oblasti [Semi-precious stone mineral reserves in the Ulyanovsk Region]. Gornyy informatsionno-analiticheskiy byulleten'. 2006, no 5, pp. 319—323. [In Russ].

3. Petrochenkov D. A. Gemmologicheskie aspekty verkhnedevonskikh yuvelirno-podelochnykh ammonitov Marokko [Gemmology of the Upper Devonian jewelry- and ornamental-quality Morocco ammonite].Doklady XII Mezhdunarodnoy nauchno-prakticheskoy konferentsii «Novye idei v naukakh o Zemle». Vol. I, Moscow, MGRI-RGRRU, 2015, pp. 321—322. [In Russ].

4. Petrochenkov D. A. Mineral'nyy sostav i strukturnye osobennosti yuvelirnykh ammonitov Kostromskoy oblasti [Mineral composition and structure of jewelry-quality ammonite in the Kostroma Region]. Izvestiya vuzov. Geologiya i razvedka. 2017, no 2, pp. 22—27. [In Russ].

5. Polyanin V. S., Polyanina T. A., Dusmanov E. N. Mineral'no-syr'evaya baza tsvetnykh kamney Rossii: perspektivy ee osvoeniya i razvitiya [Russia’s reserves of semi-precious stones: Development and expansion prospects]. Razvedka i okhrana nedr. 2015, no 9, pp. 66—76. [In Russ].

6. Collignon M. Atlas des fossiles caracteristiques de Madagascar. Fascicle IV (Argovien-Rauracien). Service Geologique, Tananarive pl. XLVII-XCV. 1959—234 p.

7. Collignon M. Atlas des fossils caracteristiques de Madagascar. Fascicle III (Oxfordien). Service Geologique, Tananarive, pl. XXXIV-XLVI. 1959—123 p.

8. Collignon M. Atlas des fossiles caracteristiques de Madagascar. Fascicle V (Kimmeridgien). Service Geologique. Tananarive, pl. XCVI-CXXXIII. 1959—137 p.

9. Grulke W. Heteromorph: The Rarest Fossil Ammonites: Nature at its Most Bizzarre 2014—224 p.

10. Kennedy W. J., Walaszczyk I., Gate A. S., Dembicz K., Praszkier T. Lower and Midle Cenomanian ammonites from Morondava Basin, Madagascar. Asta Geologica Polonica 2013. Vol. 63 (4). pp. 625—655.

11. Klinger H. C., Kennedy W. J., Grulke W. E. New and little-known Nostoceratidae and Diplomoceratidae (Cephalopoda, Ammonoidea) from Madagascar. African Natural History 2007. Vol. 3. pp. 89—115.

12. Mychaluk K. Update on ammolite production from Southern Alberta, Canada. Gems & Gemology. 2009. Vol. 45 no 3 pp. 192—196.

13. Walaszczyk I., Marcinowski R., Praszkier T., Dembicz K., Bienkowska M. Biogeographical and stratigraphical significance of the latest Turonian and Early Coniacian inoceramid/ammonite succession of the Manasoa section on the Onilahy River, south-west Madagascar. Cretaceous Research, 2004. Vol. 25, pp. 543—576.

14. Walaszczyk I., Kennedy W. J., Dembicz K., Gale A. S., Praszlier T., Rasoamiaramanana A. H., Randrianaly H. Ammonite and inoceramid biostratigraphy and biogeography of the Cenomanian through basal Middle Campanian (Upper Cretaceous) of the Morondava Basin, western Madagascar. Journal of African Earth Sciences, 2014 Vol. 89. pp. 79—132.

15. Zakharov Y. D., Tanabe K., Shigeta Y., Safronov P. P., Smyshlyaeva O. P., Dril S. T. Early Albian marine environments in Madagascar: An integrated approach based on oxygen, carbon and strontium isotopic data. Cretaceous Research, 2016. Vol. 58. pp. 29—41.

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