Scleractinian corals produce an aragonite skeleton that is usually converted to calcite by diagenetic processes after death. However, examples that have preserved the original aragonite skeleton and its original microstructure have been found in the Igualada Basin (NE Spain). The species Desmophyllum castellolense is described and analyzed. X-ray diffraction was used to confirm the skeletal aragonite and analyze the associated elements. The microstructure of the skeleton is described using polished and thin sections with the aid of scanning electron microscopy (SEM) and optical microscopy. The description of this species is taken from Álvarez Pérez, 1993, Álvarez Pérez, 1997.