A natural glass sample was obtained from the archaeological remains at Sangiran, Java where the crania of Pithecanthropus have been found. Its petrographical and chemical properties were investigated in order to determine whether this material was tektite. The analogy between the sample and tektite was readily confirmed by their morphological, structural, and compositional characteristics. This was also supported by the ₅₇Fe Mössbauer, the infrared and visible absorption spectral studies. It appears to be the oldest stone implement made of tektite, possibly an extraterrestrial material. -- AATA