Tektite are a fantastic and rare form of natural glass formed when large meteorites strike the earth. They are only created under very special, and rarely met, circumstances. Most of the time, Tektites are black, but they can also be yellow (Libyan Desert Glass) or green (Moldavite).
There are five major Tektite strewn-fields in the world, and three of them are associated with specific impact craters. The Libyan Desert Glass crater has never been found, most likely it has been covered up by shifting sand dunes. The largest Tektite strew field covers 1/3 of the Earth, but its crater has never been identified. Perhaps it is hidden under the ocean. If it’s on land, the crater is likely so huge that no one has recognized it yet!