This brief note reports the x-ray fluorescence analysis of obsidian artifacts recovered from the McGarraugh Ranch (41RB2) and Tarbox Creek (41HC2) sites in the Texas Panhandle. The obsidian specimens are distinguished by a high Niobium content. In this repsect, they are very similar to obsidian recovered from archaeological sites in the Radium Springs area of Southcentral New Mexico and a few sites in Western and Southcentral Texas. Such high Niobium obsidian appears to match obsidian from the Valles caldera, a basin in the Valles mountains west of Santa Fe New Mexico. Dating the use of High Nb obsidian is problemtatic. Associated artifacts at the McGarraugh Ranch suggest a Panhandle Aspect occupation which is generally dated at A.D. 1200 to 1450. Tarbox Creek artifacts include both Panhandle Aspect and an earlier component. The Radium Springs and other sites with High Nb obsidian are dated A.D. 900 to about 1400. High Nb obsidian may have potential as a horizon marker for this period in Texas and New Mexico archaeology.