The determination of the dielectric properties of materials is very important in the development of microwave heating systems. In this case, determining the dielectric properties of the materials to be processed is the essencial key point in order to achieve good efficiency of the system. In the present study the determination of the complex permittivity of vermiculite that is a hydrated phyllosilicate is presented. In a previous work the dielectric constant of vermiculite was determined using a TDR-based probe. In this study dielectric constant was determined through the measurement of the volumetric water content and the refractive index. Although the method demonstrated a good accuracy, it was not possible to determine the complex permittivity of the mineral due to the characteristics of the equipment used. So, in order to determine the complex permittivity using an accurate and nondestructive method, the scattering parameters were chosen. The method is based on the usage of a microstrip line and through the measurement of the S-parameters by a VNA the data was processed in MATLAB code. The results were very close to the ones obtained with the TDR probe, but now with the determination of the complex permittivity and loss tangent. The data obtained with the present study show that the determination of the dielectric properties of materials such as vermiculite using S-parameters is an accurate and nondestructive method.