Based on a novel approach that takes into account the coacervation of calcium and poly(acrylic acid) (PAA), we were able to biomimetically produce molded micropatterned parts from amorphous calcium carbonate (ACC) particles. We studied the time- and concentration-dependent growth of Ca2+/PAA coacervate droplets using dynamic light scattering (DLS) and turbidity measurements. Applying these results for the generation of high amounts of unstable ACC particles, we were able to produce slurries that could be molded into micropatterned casts. The obtained slurries contained both micrometer sized ACC particles and smaller nano-sized particles. When both types of particles were used for molding, materials with a high surface roughness could be produced, while the micropatterns of the molds could not be reproduced properly. However, by removing the bigger particles from the slurry using only the smaller, unstable, ACC particles, good reproduction of the micropatterns could be achieved, yielding smooth surfaces with a high surface area. The processing route represents a versatile platform for the bottom-up preparation of micropatterned ceramics on the basis of calcium carbonate.