We have fabricated CVD diamond windows with transmission of 71.1% at a wavelength of 10 micrometers . Raman spectra of such windows show no evidence of any luminescence or sp2 bonding and are quite similar to the spectra to that of type IIa natural diamonds. Hydrogen content of 20 ppm atomic has been determined by quantitative FTIR analysis. The thermal conductivity of this grade of diamond can be as high as 15 W/cm K, as measured by the converging thermal wave technique. We have measured bulk, shear, and Young's modulus and determined Poisson's ratio for optical grade diamond. RF dielectric constant and loss tangent measurements for lower grade diamond yielded 5.6 for the dielectric constant and 6 X 10-3 for the loss tangent.