As a planetary astronomer who has had a long career studying small bodies in the Solar System— from the dwarf planets to asteroids to moons to the rings of Saturn—I have always had an interest in meteorites, rocks from space. I have been fortunate enough to have hunted for meteorites about six times, but unfortunately have never found any. Maybe someday…. However, I have hunted more successfully for other unusual rocks.
First, here is a little background. A rock in space that orbits the Sun and is smaller than a planet or dwarf planet is called an asteroid. If it is smaller than about a meter (a little over a yard) in diameter, it is called a meteoroid. If the object looks fuzzy when viewed through a telescope, it is called a comet. Once in a while, one of these runs into the Earth. As it passes through Earth’s atmosphere, the light that we see is called a meteor or, if really bright, a fireball. If it is big enough to survive passage through the atmosphere, and we find it, it is called a meteorite.
We have meteorites from asteroids, Mars, and the Moon. There may be a class of meteorites from Mercury, but there is no agreement on this. There is general agreement that we do not have any meteorites from comets. They are just too fragile to survive passage through Earth’s atmosphere. If the incoming object is REALLY big, it will create a crater and the resulting explosion produces enormous amounts of energy. The impacting body, an asteroid or comet, vaporizes on impact, alters the surrounding rocks, and may cause a lot more damage. Ask the dinosaurs about the one that hit 65 million years ago!
One of the byproducts of these big impacts is Earth material that has been melted or vaporized, tossed out of Earth’s atmosphere, and quickly solidified as it reenters the Earth’s atmosphere. We call these impact rocks tektites. We find them in a few places around the world and in most cases we have found the impact crater associated with them. Moldavites in eastern Europe (Ries crater in Germany), Australites and Indochinites in southeast Asia and Australia (no crater conclusively identified), and Bediasites and Georgiates in southeast United States (Chesapeake Bay impact crater) are several examples.
However, there is another class of rocks that look like tektites, but have been shown compositionally and structurally not to be tektites but in fact weathered Earth rocks. When volcanic rock cools fairly quickly, it makes a dark rock called obsidian. Because it cools so quickly, it forms a glass (no crystalline structure). As this rock weathers over tens of millions of years, it absorbs some water, loses it glass-like nature, and fractures into roundish rocks that look a lot like tektites, but they are not!
To give equal time to other theories, if you Google “Saffordite,” you will find another, much more interesting origin for them. “Millions of years ago star beings from Sirius brought Saffordite to the king of the world Sanat Kumar and to the priests of Shambhala to establish on earth civilization of peace and harmony.” “It must be right, it is on the Web!”
You can purchase Saffordites on the web. Some of these sites may sell them as weathered obsidian glass and others as tektites. In either case, they are claimed to have metaphysical powers. I am not a dealer, I just collect them.
There are other similar weathered volcanic rocks found in other parts of the world. In all cases, they are chemically and physically similar to volcanic obsidian glass and not tektites.
To complete the list of pseudotektites, there are other impact rocks that have formed in place and are “just” impact-melted Earth rock that has fused into a glass. These are Libyan Desert glass found in the Libyan Desert, and Darwin glass found in Tasmania. A crater has been identified on the island of Tasmania (Australia) that appears to be the source of the Darwin glass.
Next time: the hunt is on!
This post is an annotated and serialized version of a post originally appearing on the CosmoQuest Blog.