Background: Marine environment offers a diversity of ecological resources comprising of aquatic plants and animals. Siddha system of medicine had made use of these marine organisms since antiquity. Marine enrolment became a focus of natural products drug discovery research due to its unexplored bio diversity. The potential of marine drugs as pharmaceuticals was introduced by Bergmann in 1950’s. Oxidized Pearl oyster shell has been used in the treatment of bronchitis, asthma, osteoporosis, nervous disorders, and musculoskeletal disorders in the traditional medicine. Aim and Objective: To identify and quantify the chemical composition and crystallographic structure at various stages of processing oxidized powder of pearl oyster (Muthuchippi Parpam [MCP]). Methodology: The crystalline transformations, phase purity and chemical composition of Oxidized pearl oyster shell powder (Muthuchippi Parpam), at various stages of its processing using XRD. Results: X-ray diffraction (XRD) analysis revealed a transition from a mixture of Aragonite and Calcite in the raw material to calcite (96%) in oxidized powder of pearl oyster shell. All the study sample showed crystalline structure. Conclusion: The study results conclude the concentration of calcium carbonate in the form of calcite increased in end product of oxidized pearl oyster shell powder.