Saffordite

Saffordite is a rare type of natural glass, known as pseudotectite, which was first identified in the Safford area of Arizona, USA. Unlike true tektites, which are formed by the melting of the Earth's crust during a meteorite impact, Saffordites are the result of rapid cooling of lava, resulting in the formation of a glassy structure. Saffordite is usually dark brown in colour, occasionally tinged with purple. Its occurrence is limited to certain areas in Arizona.