Aragonite-vaterite-calcite: Polymorphs of CaCO3 in 7th century CE lime plasters of Alampur group of temples, India

This paper study the occurrence of aragonite-vaterite-calcite: Polymorphs of CaCO3 in the ancient lime plaster works of south India's Alampur group of temples that was under submerged condition due to past construction of Srisailam hydroelectric dam on Tungabhadra river just nearby the temples. For the proper examination of the Alampur plaster, we used analytical methods such as onsite observation, petrological thin section, XRF, XRD, FTIR, SEM - EDX and Raman Spectroscopy. The presence of polymorphs of CaCO3 was confirmed through XRD, FTIR, SEM - EDX and Raman Spectra of the plaster. The occurrence of CaCO3 polymorphs may be due to the action of invertebrates on initial submergence, self healing of the lime due to wet and dry cycle in the presence of Mg that promoted the formation of polymorphs. Microscopic mineralogical analysis showed mixing of sub-angular to sub-rounded, medium to low maturity sand and coarse silt character aggregates of silica rich lithology. The identification of phthalocyanine blue dye in the plaster by Raman spectroscopy may be part of present day rituals. This work is a holistic approach to find out the composition of ancient lime towards protecting the sand stone masonry of the temple by applying compatible lime plasters to arrest the deterioration.