Glass from the Sky: Tektites, Museums, and Hidden Craters

Tektites are pieces of natural glass that form when a meteorite impact melts Earth rock and ejects molten droplets. Museums in Australia and in other countries have held large tektite collections that were collected over many decades, and these specimens are used for scientific study and for display. The Australasian strewn field, which includes the Australian Australites, has been dated to about 0.79 to 0.80 million years, although its exact source crater is still debated. A study published in PNAS proposed that the crater may lie buried under the Bolaven volcanic field in southern Laos, and this idea has been tested with gravity and geological evidence.

Other tektite types are much older. Tektites worldwide range from roughly 300,000 years to more than 30 million years in age, and some fields such as the North American and Libyan deposits date to tens of millions of years. In Tasmania, Darwin glass has been dated to about 816,000 years by argon-argon methods, showing that similar-age impacts can occur in different places. Therefore museum specimens can contain materials from very different events, and researchers use careful chemical analysis and radiometric dating to sort them out.