Contrasting chemical compositions in associated lizardite and chrysotile in veins from Elba, Italy
Viti, Cecilia; Mellini, Marcello
European Journal of Mineralogy Volume 9 Number 3 (1997), p. 585 - 596
published: Jun 2, 1997
manuscript accepted: Nov 27, 1996
manuscript received: Jun 20, 1996
ArtNo. ESP147050903007, Price: 29.00 €
Abstract Serpentinitic veins consisting of associated chrysotile and well crystallized lizardite were extensively sampled in the Monte Fico quarries, Elba Island, Italy. The veins are mostly formed ofeuhedral lizardite-IT. After optical, IR and X-ray characterization, the specimens were studied by transmission electron microscopy. TEM provides evidence for the occurrence of chrysotile, polygonal serpentine and lizardite, with microstructural relations pointing to a continuous recrystallization from chrysotile to polygonal serpentine and to lizardite. No major fault structure occurs in lizardite. Chemical data indicate the existence of a compositional gap between lizardite [mean composition (Mg2.79Fe2+0.09 Fe3+0.07Al0.07)Σ=3.02(Si1.91Al0.09)Σ=2.00 O5 (OH)3.90] and chrysotile [mean composition (Mg2.80Fe0.11Al0.06)Σ=2.97Si2.00 O5 (OH)4] with lizardite systematically enriched in aluminum and iron with respect to chrysotile. Therefore, the two minerals should no longer be considered as polymorphs.