If the material at the impact site consists of porous rocks rich in quartz, they will melt into a glassy mass. The molten material remaining in the crater, or its close proximity is highly chemically inhomogeneous and takes different shapes. These stones are called impact glasses or impactites for short.
Libyan and Darwinian glass
The most famous impactite is the Libyan glass, found on the border of Libya and Egypt. in the area of the so-called Great Sand Sea. It occurs in irregular, often large pieces, which indicate a very short transport. However, the source crater has not yet been confirmed. Maybe it is hidden beneath the dunes of the great sand sea. This natural glass was already known and used by the ancient Egyptians, and it was highly valued, as demonstrated by Tutankhamun’s jewellery featuring a yellow scarab made of Libyan glass in the middle. The Darwinian glass from the vicinity of the Darwin crater in Tasmania is probably also an impactite.
In the oblique direction of flight, the pressure wave in front of the meteorite can melt the surface layer of rock and eject it still in a liquid state, hundreds to thousands of kilometres away from the crater. This happens just before the actual body of the meteorite hurtles into the ground causing a huge explosion.
In the meantime, pieces of the hot melt that are rather homogeneous (clean) solidify in flight through the air or just after falling to the ground again. These stones are called tektites, and the land they fall on is referred to as a “fall field.”
According to the impact areas that are always associated with a particular meteorite impact event, we find:
North American tektites
The oldest known are North American tektites, georgianites and bediasites, some 35.4 million years old. Apparently associated with the formation of a massive crater beneath today’s Chesapeake Bay.
Central European tektites (vltaviny, internationally known as moldavites)
The most beautiful tektites are undoubtedly moldavites, which are the only ones in the world characterized by perfect clarity and many shades of the colour green. They flew through the air to Bohemia from the Ries crater in today’s Bavaria about 15 million years ago.
African tektites (ivorites)
Ivorites come from the Bosumtwi crater in Ghana, Africa. These stones flew through the air, regardless of today’s political boundaries, and are on the territory of a different state than the crater they originally came from. As their name suggests, they landed on the territory of today’s Ivory Coast.
Australasian tektites
The youngest, and at the same time the largest in both number and size, are the Australian tektites, which are found on a large area of Southeast Asia and Australia. They are usually designated according to the more specific area of the discovery, such as indochinite, billitonite, filipinite, javaite, australite, etc. The crater they originate from has not yet been discovered, but it is known that it was created about 760,000 years ago.