Vaterit in Süßwasser-Zuchtperlen aus China und Japan

WEHRMEISTER, URSULA; JACOB, DORRIT E.; SOLDATI, ANALIA L.; HÄGER, TOBIAS; HOFMEISTER, WOLFGANG

Zeitschrift Deutsche Gemmologische Gesellschaft

Año: 2007 vol. 56 p. 99 - 118

Japanese and Chinese tissue and bead nucleated cultured freshwater pearls of good quality were investigated with Raman spectroscopy and LA-ICP-MS. In 50% of the investigated tissue nucleated samples vaterite could be identified by Raman spectroscopy in polished cross-sections near the centre of the cultured pearl as well as in little blemishes on the cultured pearl surfaces. Continuous growth structures transect both vaterite and aragonite areas. Sodium and strontium concentrations are significantly lower in vaterite areas whereas the Mg concentration is up to two orders of magnitude higher and allow distinction of the two phases with trace element analytical methods (e.g. LA-ICP-MS). The high amount of high quality cultured pearls with vaterite in their centre as well as the findings of vaterite in lacklustre cultured pearls implies that the formation of vaterite during cultured pearls growth may be a major factor in affecting the quality of freshwater cultured pearls.