Procedures for the growth and doping of calcite crystals in gel systems are described. Crystals surrounded by gel tend to incorporate the silica network with its structure intact. Hybrid methods avoid this contamination. Crystals then grow in small volumes of solution, the solution being replenished by diffusion through gel filtering media. The solution cavities can be seeded with calcite crystals which then serve as substrates for epitaxial growth. Weight increases by factors up to 10 are easily achieved.