Identification of Bio-Minerals and Their Origin in Lime Mortars of Ancient Monument: Thanjavur Palace

The role of organics in ancient mortars of Thanjavur palace was characterized through wet chemical analysis, biochemical tests and sophisticated techniques (XRD, FESEM, FT-IR). All the analytical techniques confirm the presence of all the polymorphs of calcium carbonate with vaterite as a major mineral followed by calcite and aragonite minerals. A part from calcium carbonates, calcium oxalates were noticed in the form of film in FESEM which was supported by XRD and FT-IR. The presence of calcium oxalates in lime mortars was due to the interaction of organic compounds with bacterial species. The confirmation came through 16s rRNA molecular characterization, the bacterial colonies bacillus cereus, Pseudomonas stutzeri, was identified. These strains are capable of producing oxalic acid in the presence of plant extracts and are also responsible for initiation of biominerals in lime mortar. FT-IR and organic tests substantiated the presence of carbohydrates and proteinous compounds present in the mortars. Carbohydrate content in organics is responsible for increased carbonation. The chemical analysis indicates the hydraulic nature of lime with 30% of clay.