The optical absorption properties of Co60‐irradiated fused silica and crystalline quartz have been studied in the vacuum‐ultraviolet region. The most prominent absorption band found in both materials has a maximum at 7.6 ev (1620 A). Optical and thermal bleaching experiments indicate that this band is not necessarily complementary to a band at 5.9 ev (2100 A), as has been assumed. Though the 7.6‐ev band has approximately the same intensity in both materials for the same irradiation, the 5.9‐ev band is >20 times more intense in fused silica. The 7.6‐ev band is still present after the 5.9‐ev band has been thermally bleached. Additional absorption bands occur at 8.0 and 8.2 ev. Also, optical and thermal bleaching experiments suggest other absorption bands at 7.2, 7.4, 7.8, and 7.9 ev. Since these bands (particularly the 7.6‐, 8.0‐, and 8.2‐ev bands) occur in high‐purity silica and quartz, it is suggested that they are associated with defects in the quartz structure and are not caused by impurities.