  Rock is a complicated material because of the inherent heterogeneity in
mineral phases and composition, even when extracted from the same rock mass.
The spatial variability in compositional and structural features prevent
reproducible measurements of deformation, fracture formation and other physical
and chemical properties. Here, we use geo-architected 3D printed synthetic
gypsum rock to show that mineral texture orientation governs the isotropy or
anisotropy in fracture surface roughness and volumetric flow rate through
tensile fractures. Failure load is governed by the orientation of depositional
layering relative to loading direction but this effect can be hidden when an
orientated mineral texture is present within the layers. We find that samples
with certain mineral orientations are twice as strong as the weakest samples
and that high values of sample strength correlate with rougher fracture
surfaces. Mineral texture oriented parallel to the failure plane gives rise to
anisotropic surface roughness and in turn to anisotropic flow rates. The
uniqueness of induced fracture roughness and the degree of anisotropy is a
potential method for assessment of the orientation and relative bonding
strengths of minerals in a rock. With this information, we will be able to
predict isotropic or anisotropic flow rates through fractures which is vital to
induced fracturing, geothermal energy production and CO2 sequestration.
