ABSTRACTSamples of ancient Roman glass taken from burial vaults on the Island of Cyprus have been examined. Analysis shows the glass to be of the soda‐lime type characteristic that period. The heavy incrustation produced by weathering has been studied spectroscopically and microscopically and is shown to consist, for the most part, of hydrated silica, formed by the slow hydrolytic decomposition of the glass. The beautiful iridescence exhibited by the glass is due to the selective destructive interference of light the thin films of transparent incrustation on the surface of the glass.