Crystals of the beryl variety morganite, hosted in a pegmatitic dike of the Island of Elba were analyzed by standard gemological methods, LA-ICP-MS, single crystal XRD and spectroscopic methods. The samples show a stubby and tabular shape, appear transparent, pastel colored and light in tone with different shades of color: very light pink, light pink, pink. The structure refinement showed a reduced replacement in the octahedral and in the T2 tetrahedral sites. The most abundant elements are Al (around 7%) and Be (around 5%), followed by the alkali and earth alkali metals Cs (around 5100 ppm), Na (around 2700 ppm), Ca (1600 ppm), Li (around 1400 ppm), Rb (240 ppm) and K (150 ppm). The total of alkali metals is around 1.1%, so that morganites plot in class 5 of the classification by CERNY (1975). Cs generates the UV luminescence. Alkali elements are interpreted as hosted into the strctural channels of the minerals. Mn is the most important chromophore element and responsible for the pink color. The high contents of earth alkali and alkali metals indicate that morganite formed during the late stage of pegmatitic evolution with a possible influence of carbonate country rocks.
Gem-quality morganite from Monte Capanne pluton (Elba Island, Italy)
CAUCIA, FRANCA PIERA;MARINONI, LUIGI TITO;CALLEGARI, ATHOS MARIA;LEONE, ALBERTO;
2016-01-01
Abstract
Crystals of the beryl variety morganite, hosted in a pegmatitic dike of the Island of Elba were analyzed by standard gemological methods, LA-ICP-MS, single crystal XRD and spectroscopic methods. The samples show a stubby and tabular shape, appear transparent, pastel colored and light in tone with different shades of color: very light pink, light pink, pink. The structure refinement showed a reduced replacement in the octahedral and in the T2 tetrahedral sites. The most abundant elements are Al (around 7%) and Be (around 5%), followed by the alkali and earth alkali metals Cs (around 5100 ppm), Na (around 2700 ppm), Ca (1600 ppm), Li (around 1400 ppm), Rb (240 ppm) and K (150 ppm). The total of alkali metals is around 1.1%, so that morganites plot in class 5 of the classification by CERNY (1975). Cs generates the UV luminescence. Alkali elements are interpreted as hosted into the strctural channels of the minerals. Mn is the most important chromophore element and responsible for the pink color. The high contents of earth alkali and alkali metals indicate that morganite formed during the late stage of pegmatitic evolution with a possible influence of carbonate country rocks.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
