Chemical gardens are self-assembled tubular structures formed via abiotic precipitation upon the interaction of metal-ion salts with aqueous solutions of anionic species such as silicate, carbonate, or phosphate. These tubular structures have been suggested to be relevant for the early Earth and Earth-like planets and moons where alkaline silica and carbonate rich soda oceans are thought to be widespread. Carbonate and silica gardens are believed to be forming under the geochemical conditions of these soda oceans. Silica gardens are self-compartmentalized compositionally distinct bilayered mineral membranes. These membranes are small batteries that selectively catalyze the synthesis of prebiotically relevant organic compounds such as carboxylic acids, amino acids, and nucleobases by condensation of formamide. Recently, we have grown chemical gardens and mineral vesicles by immersing different metal salts in soda lake water and inferred that mineral self-organization could be a plausible scenario on soda oceans of early Earth and extraterrestrial planets and moons such as Enceladus. In this work, we have performed in-situ monitoring of the chemical gradient, pH and electrochemical potential differences across macroscopic calcium carbonate tubular structures grown by immersing calcium chloride salt pellets in carbonate-rich soda lake water (Lake Magadi, Southern Kenyan Rift Valley). To understand the temporal evolution of the growth process, we have performed ex-situ X-ray diffraction, Raman and infrared spectroscopy, and scanning electron microscopy of the tubular structures isolated after different periods of growth. We have also compared our results with calcium carbonate and silica gardens grown in model laboratory solutions. The walls of calcium carbonate tubular structures are composed of bilayers of texturally different but mineralogically similar crystalline calcite. We have observed that pH gradients across these “natural” calcium carbonate tubes are comparable to that of silica gardens and higher than that of synthetic carbonate gardens. We have discussed the implications of the texture, ionic gradient, pH and electrochemical potential differences across the tubes to material sciences, prebiotic chemistry, and origin of life.