We describe a novel artificial dielectric material that has applications at millimeter and submillimeter wavelengths. The material is manufactured from layers of metal mesh patterned onto thin polypropylene sheets, which are then bonded together using a hot pressing process to provide planar rugged discs that can be reliably cycled to cryogenic temperatures. The refractive index of this material can be tuned by adjusting the geometry and spacing of the metal mesh layers. We demonstrate its usage by designing and characterizing a broadband antireflection coating for a Z-cut crystalline quartz plate. The coating was fabricated and applied to the quartz using the hot press technique and characterized using a Fourier transform spectrometer. The performance is shown to be in good agreement with a high frequency structure simulator and transmission line modeling results.