Oscillatory zoning of solid solution of (Ba,Sr)SO4 was investigated in gelatin. Then, Ba2+ and Sr2+ diffused into gelatin, and SO42- also diffused from opposite side. Periodic change of molar ratio Ba2+/Sr2+, which was firstly found out by Putnis et al. (1992) in silica gel, was well reproduced. However, we were able to obtain fine-structured particles which are quite different from those in silica gel. We investigated effects of gelation time and gelatin concentration on the structure and chemical inhomogeneity of particles. Experiments with 16% and 24%-gelatin gave results that core portion of solid solution was composed of BaSO4, which was different from the results in silica gel. Furthermore, we were able to make various kinds of particles with novel structures by controlling gelation time and gelatin concentration. For example, different structures of particles were successfully formed in separated zone in gelatin. As another, white turbid zones containing particles were clearly separated by a transparent gel. These particles were formed spontaneously without special operations. This was achieved by a reaction-diffusion mechanism. Gelation time and gelatin concentration controlled the diffusion rate mainly, which induced dramatic change in particle growth process in gel. On the basis of these findings, we discussed the mechanism of particle growth in this system.