The bicontinuous lyotropic liquid phases surrounded by the isotropic phase form monocrystals with well-developed facets. We investigate the structure and stability of the facets formed by the bicontinuous phase of Pn3̅m symmetry, at three preferred directions, which are developed on a spherical droplet of Pn3̅m phase surrounded by the isotropic phase. The structure of the facets is obtained by minimization of the Landau-Brazovskii functional with one scalar order parameter.