Optical operations have served as the basis of spectroscopy and imaging in terahertz regimes for a long time.Available lenses are practical tools for modulations.We fabricate a kind of biconvex lens from the natural dolomite cluster.The lens works well at 0.1 THz based on the relatively high refractive index and low absorption coefficients.Compared with the lens fabricated by a dolomite stone,such a lens can focus dispersive terahertz beam efficiently in terahertz imaging systems,which indicates that natural minerals hold promising applications in terahertz optics.