This paper reports an electric birefringence study on dilute solutions of the clay mineral, celadonite. The results show that celadonite particles in solution have the form of rectangular platelets and are characterized by a permanent dipole-moment perpendicular to the plane of the platelet and an induced dipole-moment in the plane of the platelet along the longest dimension. It is suggested that the permanent dipole-moment is an inherent property of the atomic structure of the platelet, whilst the induced dipole-moment is a consequence of the ion-atmosphere surrounding the celadonite particles. The paper also demonstrates the usefulness of electro-optic techniques in studying problems in clay minerology.