ANALYZING THE GROWTH AND FORM OF MOLLUSK SHELL LAYERS, IN-SITU, BY CATHODOLUMINESCENCE MICROSCOPY AND RAMAN-SPECTROSCOPY

We describe two novel methods to analyze the microstructure of mollusc shell layers in situ in shell sections. Living abalone, Haliotis rubr a (Leach), were immersed in seawater baths to which manganese chloride tetrahydrate was added. Distinct cathodoluminescent marks were produc ed within shell layers formed during the immersion period. Electron an d proton microprobe analysis of shell sections confirmed that concentr ations of manganese ions within aragonitic and calcitic shell layers a re associated with yellow-green and orange-red luminescence, respectiv ely, which allows us to distinguish mineral types. Colored cathodolumi nescent marks within shells show that the mineralization of aragonite and calcite may occur simultaneously in the prismatic layer, but also that mineralization under one area of the mantle may switch between po lymorphs over short periods. Using cathodoluminescent marks, we show t hat Raman laser spectroscopy can distinguish mineralogical types in si tu and that the dark nacreous layers, variously described as ''growth checks'' or conchiolin layers, contain aragonite rather than calcite.