Did the earlier human-like species Homo erectus see the storm of tektites? This reconstruction from the Museum of Archaeology, Herne, Germany. Credit: Wiki

800,000 years ago the sky over Asia was aflame with teardrops of molten earth, blasted heavenward by a gigantic meteorite impact. Members of Homo erectus, a precursor to modern humans, must have seen the firestorm and gone running for shelter.

What lit the terrified eyes of our distant ancestors were splatters of liquified rock catapulted high into the atmosphere immediately after the impact. This fiery rain cooled and solidified into wondrous and diverse forms as it fell back to Earth as the black rocks we know today as tektites.

Scientists still don’t know where the impact occurred, but it left a huge butterfly pattern of tektites spread across China, southeast Asia and southern Australia.

A variety of tektites ranging from an inch to 2.5 inches from southern China. Photo: Bob King

Tektites are not meteorites but rather Earth rocks that were liquified by the heat and pressure of impact and launched into the atmosphere, even as far as nearby outer space. They’re essentially local rock converted to glass.

Tektites resemble volcanic obsidian, that shiny black glass you find in mineral shops, but they’re a very different material. Composed mostly of silica, commonly found in nature as sand or quartz, the extreme heat they experienced, combined with passage through the rarefied upper atmosphere, have made tektites one of the driest materials found on Earth. Some tektites contain minute amounts of the original meteorite, but what really catches your eye are their shapes and textures.

Tektites, from the Greek for "molten", come in a wide variety of shapes depending on how far they were ejected and how they spun as they rained back to Earth. From left: an oval "hamburger patty", sphere, dumbbell, a hollow-centered ball and teardrop. The grooved surface textures, described below, are unique to tektites. Photo: Bob King

As the cooling but still plastic blobs fell back through the lower atmosphere, they were deformed by friction with the air into a variety of different shapes depending upon their spin. Spheres or balls formed from material spinning evenly in all directions. Blobs spinning or rotating in just two directions or axes stretched to produce oval-shaped tektites. Ovals were further stretched into dumbbells, and dumbbells snapped apart to create pairs of elongated teardrops. Click HERE for a great illustration of how tektite shapes form.

The backside of a beautiful flanged button tektite from Australia. It measures about 3/4" across. The shape of these buttons served as a model for heat shields on NASA space capsules like Mercury, Gemini and Apollo. Credit: Herbert Raab

Tektites ejected to great height at distances of 2,500 to 3,700 miles from ground zero had enough time to solidify. Falling back to Earth they melted again to produce exquisite little buttons surrounded by circular flanges. These rare forms are typically found in Australia far from the center of what’s known as the Australasian tektite strewfield.

Tektites developed fine cracks as they cooled upon reentry which were later enlarged into zillions of pits and grooves through interaction with water and soil in a process called chemical etching. They give these shiny rocks lots of character. Some tektites have smooth sides from material that flaked off after they cooled.

Flow lines in this tektite show us in a very graphic way that tektites were once soft and plastic. Photo: Bob King

While the Australasian tektites are the most recent and largest strewnfield, there are several other major tektite localities both with and without associated craters:

* North American strewnfield with tektites primarily found in the southeastern states and in Texas. Source: Chesapeake Bay Crater impact 34 million years ago
* European strewnfield famous for the green glass called moldavite, the most colorful of the tektites. Source: Ries Crater impact in Germany 15 million years ago
* Ivory Coast strewnfield originating from the Lake Bosumtwi Crater impact in Ghana 1 million years ago
* A new strewnfield recently discovered in Belize

Part of this tektite is thin enough to let light through and show color in the glass. Photo: Bob King

The most common tektites are those from China and southeast Asia. You’ll find several online sites offering them for sale. One of the best is The Tektite Source run by Norm and Cookie Lehrman. eBay has many dozens for sale every day.

A broken or chipped tektite will help you appreciate both their glassy quality and color. Some are translucent enough to show shades of brown and olive green. All of them have a certain enigmatic aspect. I like to pick one up, turn it in my hand and try to fathom the origin of this or that feature.

Closeup showing numerous pits and grooves. The radial lines were formed when the tektite hit the ground upon landing. Photo: Bob King

It used to be thought that tektites might have been blasted off the moon during a lunar impact or even volcanically, but their earthly composition, traces of meteoric materials and association with craters on Earth connect them to catastrophic events right here at home. To learn more about these cool rocks, I recommend a visit to Aubrey Whymark’s tektite site.