Abstract: A fiber reinforced glass composite capable of absorbing or transmitting microwave radiation includes refractory fiber in a matrix of a black glass ceramic having the empirical formula SiCxOy where x is greater than zero and up to about 2.0, and y is greater than zero and up to about 2.2. Preferably, the black glass ceramic is made by pyrolyzing precursor polymers derived from cyclosiloxane monomers containing a vinyl group attached to silicon and/or a hydride-silicon group in a controlled atmosphere, thereby adjusting the dielectric properties.