Abstract: During the recent regional geological survey, a nonmetallic ore source—obsidian was found in the Sumdo area of Jongbo Gyamda County, Tibet. The obsidian source originated from the Cenozoic Nianbo Formation in the Gangdise terrane. The bulb structures are clearly visible, and some obsidian stones have reached the gem level. A preliminary study was undertaken and the result reveals that the obsidian was derived from partial melting of the crust. Although the polymetallic ore deposits are common in the Gangdise metallogenic belt, the discovery of Sumdo obsidian has not only delineated a nonmetallic ore spot but also provided important clues for regional follow-up prospecting work and archaeological study.