The Brillouin scattering spectra of crystalline quartz, fused quartz and Pyrex glass have been observed. The crystalline quartz spectrum contains three doublets corresponding to one longitudinal and two transverse acoustic modes, whereas the spectra of used quartz and Pyrex glass have one longitudinal and one transverse component each, as is expected for isotropic solids. From the lack of observable broadening of any of the Brillouin components, it is concluded that the room temperature attenuation coefficient &agr; of both longitudinal and transverse phonons at 10 to 20 Gc is less than 103cm−1.