Pica glass

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Pica glass, also called Atacama desert glass, is impact glass found along a long stretch of the Atacama Desert in northern Chile near the town of Pica. The glass is very light and often has folds, twists, and flowing patterns. Pieces can be as large as 50 cm across. Scientists think it formed when a comet exploded in the air above the desert around 14,000 to 12,000 years ago, during the Late Pleistocene. The event happened soon after humans first arrived in South America, so some early hunter-gatherers may have seen it.