Terahertz spectroscopy of natural stone materials

Using terahertz time-domain spectroscopy (THz-TDS), we measured optical constants of nine different types of common natural stones: slate, gneiss, marble, mudstone, sandstone, dolomite, granite, tuff, and diorite. The result shows that most natural stones are fairly transparent in THz frequency range, and dolomite, in particular, exhibits a nearly uniform refractive index of 2.7 over frequency range from 0.2 to 1 THz. The high refractive index of dolomite is comparable to silicon, and a fabricated dolomite THz lens shows an applicable performance.