Twenty samples of natural glasses (volcanic glasses, impact glasses, tectites and fulgurites) are described and compared with twenty artificial glasses and ceramics proposed for packing of high level radioactive waste. The weathering indices tested both groups of samples. There is a negative correlation between the sum of net-forming oxides and the weathering index I_ko (and IPW or I_w). According to these indices, Pyrex is the synthetic glass which is the most resistent to weathering. It has an analogue in the Libyan Desert glass. Some pairs of both natural and synthetic types of glass have been found with similar values of weathering indices. On the basis of comparison of the weathering stability of various natural glasses and glasses used for vitrification, the following glasses have the highest stability as suitable natural analogues: an obsidian, tectites and the Libyan Desert glass.