Materials like bivalve shells and coral reef stone constitute the majority of plastering mortar type of old fortifications from Cartagena city, Colombia. A physical-chemical and spectroscopic material (oyster) study of Crassostrea Rizhophorae (CR) and Pinctada Radiata (PR) was performed to find their surface bioreceptiveness and synthesize more resistant mortar to the deteriorating. The XRD analyzes show calcite dominant presence in CR and aragonite traces by PR specie, which presented greater absorption of metals Fe and Mn, being indicative of contamination. Organic impurities and CaO formation at 790°C was found by TGA for CR and 630°C for PR. Materials showed low surface area and microporosity.