Archaeological Research Facility

The analysis here of six vitreous rock samples indicates trachy-andesite and basaltic trachy-andesite glasses according to an alkali/silica plot (Le Bas et al. 1986; Le Maitre et al. 1989; Table 1 and Figure 1 herein). Trachyte glass does occur in nature such as the Emuruangogolok volcano in Kenya, and a source in the Hawai'ian Islands, the former with SiO2 values over 62% by weight (Steve Lundblad, personal communication; Weaver 1977).