Gem-quality tourmaline from LCT pegmatite in Adamello Massif

database, nuove specie, discrediti,
ridefinizioni, classificazioni, ecc.
Rispondi
Avatar utente
Marco E. Ciriotti
Messaggi: 24995
Iscritto il: ven 25 giu, 2004 11:31
Località: via San Pietro, 55 I-10073 Devesi/Cirié TO - Italy
Contatta:

Gem-quality tourmaline from LCT pegmatite in Adamello Massif

Messaggio da Marco E. Ciriotti » ven 14 dic, 2018 11:41

Referenza:
▪ Diella, V., Pezzotta, F., Bocchio, R., Marinoni, N., Cámara, F., Langone, A., Adamo, I., Lanzafame, G. (2018): Gem-Quality Tourmaline from LCT Pegmatite in Adamello Massif, Central Southern Alps, Italy: An Investigation of Its Mineralogy, Crystallography and 3D Inclusions. Minerals, 8, 593; https://doi.org/10.3390/min8120593

Abstract:
In the early 2000s, an exceptional discovery of gem-quality multi-coloured tourmalines, hosted in Litium-Cesium-Tantalum (LCT) pegmatites, was made in the Adamello Massif, Italy. Gem-quality tourmalines had never been found before in the Alps, and this new pegmatitic deposit is of particular interest and worthy of a detailed characterization. We studied a suite of faceted samples by classical gemmological methods, and fragments were studied with Synchrotron X-ray computed micro-tomography, which evidenced the occurrence of inclusions, cracks and voids. Electron Microprobe combined with Laser Ablation analyses were performed to determine major, minor and trace element contents. Selected samples were analysed by single crystal X-ray diffraction method. The specimens range in colour from colourless to yellow, pink, orange, light blue, green, amber, brownish-pink, purple and black. Chemically, the tourmalines range from fluor-elbaite to fluor-liddicoatite and rossmanite: these chemical changes occur in the same sample and affect the colour. Rare Earth Elements (REE) vary from 30 to 130 ppm with steep Light Rare Earth Elemts (LREE)-enriched patterns and a negative Eu-anomaly. Structural data confirmed the elbaitic composition and showed that high manganese content may induce the local static disorder at the O(1) anion site, coordinating the Y cation sites occupied, on average, by Li, Al and Mn2+ in equal proportions, confirming previous findings. In addition to the gemmological value, the crystal-chemical studies of tourmalines are unanimously considered to be a sensitive recorder of the geological processes leading to their formation, and therefore, this study may contribute to understanding the evolution of the pegmatites related to the intrusion of the Adamello pluton.

NdR: Una preliminare descrizione del ritrovamento è in:
Pezzotta, F. & Guastoni, A. (2002): Adamello: La pegmatite LCT della valle Adamè. Rivista Mineralogica Italiana, 26, 127-142.
Marco E. Ciriotti

«Things are interesting only in so far as they relate themselves to other things»

Avatar utente
TOSATO FABIO
Messaggi: 6270
Iscritto il: ven 13 gen, 2006 11:39
Località: via A.Cantele n.15 35129 PADOVA

Re: Gem-quality tourmaline from LCT pegmatite in Adamello Massif

Messaggio da TOSATO FABIO » ven 14 dic, 2018 16:00

Complimenti agli autori e scopritori del luogo.
Tosato Fabio
"Il vero viaggio di scoperta non consiste nel cercare nuove terre, ma nell'avere nuovi occhi." M. Proust
Noi siamo anche quello che non siamo riusciti ad essere.
Sic transit gloria mundi.

Rispondi

Chi c’è in linea

Visitano il forum: Bing [Bot] e 5 ospiti