Effect of inorganic additives on the growth of silica-carbonate biomorphs

Silica-barium carbonate biomorphs are complex precipitate microstructures that form by purely inorganic processes. They display life-like morphologies with smoothly curved surfaces that are not restricted to crystallographic symmetries. We investigate the morphogenetic influence of inorganic dopants that compete with the barium carbonate precipitation. Trace deposition of alkaline earth or transition metal additives causes significant changes to the crystal morphologies. In the case of Pb2+ and Ag+ ions, biomorph growth is disrupted by the formation of competing precipitates. Similarly, the addition of Ca2+, Mg2+, and Zn2+ induces the rapid crystallization of witherite or amorphous silica-carbonate aggregates at enhanced growth rates. By comparison, the addition of strontium ions results in the assembly of classic biomorphs such as cardioid sheets and helices. The procedures reported here exemplify the use of co-depositing agents to influence the compositional and crystallographic properties in a manner similar to magnesium-doped biogenic calcites.