This paper reports on a new type of composite nanoparticle consisting of a calcite (CaCO3) core and a silica (SiO2) shell. The cubic core-shell particles were created using a surface precipitation procedure using cubic calcite as seeds on which a silica layer was grown. Moreover, the calcite of core-shell nanoparticles can be dissolved leaving silica shells. The characterizations of composite and silica shells were made by using TEM, BET, XRD, IR, XRF, and TGA. The results show that the silica layer was continuously coated on the surface of CaCO3 core with a thickness of about 5 nm. After coated with silica shells, the thermal stability decreases for its reaction with silica. The shape and size of pores of silica shells were similar to that of the CaCO3 cores. (C) 2004 Elsevier B.V. All rights reserved.