In biomineralization, organisms actively build structures (e.g., bones) or initiate a reaction from the secretion of precipitation-inducing chemicals (e.g., stromatolites). Even within extreme temperature and pH environments, bacteria-induced mineral precipitation uses enzyme-mediated reactions and/or controls the surrounding metal redox state to create dense mats of mineral filaments. While inorganic reactions are capable of mimicking these morphologies, such as laboratory grown chemical gardens, biominerals are often composed of mineral phases that are seldom selected in inorganic precipitation. Complicating the understanding of mineral selection in extremophiles versus similar inorganic counterparts is the large variation between their environmental conditions during precipitation. Using temperature/pressure vessels, I will investigate biominerals formed by thermoacidophiles and thermoalkaliphiles and compare their crystal products to those of chemical gardens formed under the same conditions. The goal is to understand the distinction between precipitation in living versus nonliving systems including the modification of crystal structure and habit within the silica-rich environments where both structures are found as well as the effect of metabolic processes on existing inorganic and biomineral structures. Tackling knowledge gaps in extremophiles will provide insights into the mechanisms for biomineralization and survival of these organisms in mineral-rich environments (at toxic levels for most organisms). This work can also pave the way to understanding how life could withstand the harsh conditions of early Earth and current conditions on other planetary bodies.