Crystal chemistry of piemontites: REE-bearing piemontite from Monte Brugiana, Alpi Apuane, Italy
Bonazzi, Paola; Garbarino, Carlo; Menchetti, Silvio
published: Feb 13, 1992
manuscript accepted: May 14, 1991
manuscript received: Jul 14, 1990
ArtNo. ESP147050401004, Price: 29.00 €
Abstract An unusually REE-rich piemontite was found near Colonnata on the northern slope of Monte Brugiana and La Rocchetta, Alpi Apuane, Italy. Quantitative chemical analyses show a total amount of rare earth elements ranging from 2.85 to 8.06 (oxides wt%) with lanthanum prevailing on the others. Structural data obtained on four single crystals show that the atomic arrangement is, on the whole, similar to that of REE-free piemontites. Differences arise mainly from the entry of divalent cations in the M3 octahedral sites and, to a lesser extent, in Ml. The Ca ⇄ REE substitution takes place in A2, as in allanite, while the Al site is interested by the entry of Mn2+ substituting for calcium.