Structural peculiarities of jewelry mother-of-pearl Hauterivian ammonites from the Ulyanovsk region

Petrochenkov D. A.

Zapiski RMO (Proceedings of the Russian Mineralogical Society). 2018. V. 147. N 4. P. 108-113

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Language: Russian


Fossil mother-of-pearl Hauterivian ammonites from Ulyanovskaya area with dark red, less often orange and rarely green iridescent are widely used in jewelry. Irisation of fossil mother-of-pearl is determined by original aragonite layers of the walls of ammonite shells. These layers are formed by aragonite microcrystals 2—3 mkm width and 0.15—0.3 mkm thickness. Size and degree of ordering of aragonite microcrystals in the layer determine the irisation color. It have been revealed that aragonite microcrystals were disintegrate into aragonite globules with 4—20 nm radius in the initial stage of diagenesis process.

Key words: ammonites, fossil mother-of-pearl, aragonite, structure, iridescent, jewellery-decorative stones, Ulyanovsk region.