Long-lived spectral holeburning has been observed in Eu3+ and Pr3+ doped silicate glasses, and used to measure homogeneous linewidths (φh). In the case of Eu3+, holes are burned by optical pumping of nuclear quadrupole levels, and our low temperature measurement of φh shows that the previously determined T1.8 temperature dependence holds down to at least 1.6 K. On the other hand, in Pr3+ doped glass, holes are burned by optically induced local lattice rearrangements. In contrast to previously studied inorganic glasses, we find a linear temperature dependence of φh for the 3H4 ↔ 1D2 transition from 1.6 K to 20 K. This was confirmed by picosecond accumulated grating photon echoes. Current theories of dephasing in glasses do not predict these temperature dependences. Holeburning has also been observed in Pr3+ doped BeF2 and phosphate glasses and Nd3+ doped silicate glass and thus appears to be a rather general phenomenon in inorganic glasses, as has been found for molecules in organic glasses. © 1983.