Layer silicates (phyllosilicates) are important minerals because of their ubiquity on the Earth’s crust and due to their ability to release water in the mantle. The present study focuses on the elastic properties of a specific phyllosilicate known as phlogopite [KMg₃Si₃AlO₁₀(OH)₂], which were characterised using first-principles methods. The results show the mineral's anisotropic mechanical behaviour, which also depends on how the mineral layers are stacked in the crystal structure.