This work surveys the properties of materials at 1.3 um. The interest in this wavelength has been generated by the development of second generation optical fibers and by the development of the iodine (I*) laser, which operates at 1.315 um. Most of the data reported here were taken by Nd:YAG lasers modified to operate at 1.319pm. Spectral scans of some less common materials are presented. The effective optical absorption coefficient Beff measured by laser rate calorimetry is given for all materials. The thermo-optic coefficient an/aT at 1.3 um is given for a number of materials. If 1.3 um results are lacking, values at 1.15 um are given. Among the lower absorbing materials are KCI, LiF, NaCI, CaF2, SiO2, YLF (LiYF4), sapphire (Al203), MgF2, BaF2, and Q-98 phosphate glass. Results on a number of Schott infrared and laser glasses are given, including LG-670, LG-660, LG-750, LG-810, LG-760, LG-680, IRG-7, IRG-9, IRG-3, and IRG-N6. Results are given also on ZnS (normal and water clear), YAG (Y3A1501 2), ZrO2, SrF2, ZnSe, MgO, and CdTe. Some other glasses studied were hafnium fluoride glass, As2S3, CORTRAN 9753 and 9754, and Barr & Stroud calcium aluminate glasses BS 39B and BS 37A. The ten lowest absorbing materials had effective optical absorption coefficients Leff between 0.13 and 0.5 X10-3 cm-1. The lowest a n/aT value measured was 0.06X10-5/°C on Schott LG-660 alkali-Zn-silicate glass.