Brazil hosts a newly discovered field of natural glass made from meteorite impacts, according to a new study.
The natural glass is known as a tektite, which occurs after terrestrial rocks are melted when meteorites, cometsor asteroids strike into the surface of our planet, according to Encyclopedia Britannica. (The word “tektite” is derived from Ancient Greek words it means “melted” or “melted”.)
“Tektites … are known to occur in only five different scattered fields on Earth,” the researchers wrote in a December 2025 paper in peer-reviewed journal Geology.
“We report the discovery of a new tektite strewn field in northeastern Brazil. This recent discovery resulted in the collection of ~500 samples found within a strewn field at least 90 km (56 miles) long,” added the study, which was led by Álvaro Penteado Crósta, a geologist and senior professor at the Institute of Geosciences Campinas.
Scientists suggest the impact occurred about 6.3 million years ago, based on radioactive dating of argon isotopes. For context, it was at the end of the Miocene epoch, which is about when we can start tracking people as a distinct species.
Why are tektites so rare?
Because meteorites can strike anywhere Earthone would think molten glass would be more common. However, the story of the drug is a little more complicated than that.
First, we need to consider the composition of the underlying rock: shale and quartz sandstone, or some types of igneous rock, for example. “Most current scientists theorize that tektites form by rapid heating and subsequent cooling of quartz-rich soils and rocks,” according to a statement from experts at the Jackson School of Geosciences at the University of Texas.
Second, size matters: Large meteorites are more likely to produce the necessary melting. “The impact of large meteorites with the Earth’s surface provides enough energy to melt soil and rocks and spread the molten ejecta from these impacts over great distances, forming tektites,” the statement said.
On Earth, zones of tektites are distributed in “strewn fields” that include “specimens similar in age and chemical composition,” and can be found either on the Earth’s surface or underwater in deep-sea sediments (known as “microtektites”).
The largest scattered field is known as the Australasian, which covers about 10% of the Earth’s surface. Other examples are in the Ivory Coast, the Czech Republic and North America.
Distinctive name
It is common in the tektite community to give each type of tektite its own name, based on where it was found. An example is “modavites” in the Czech Republic, which comes from the Vltava (or Vltava) River in Bohemia.
The recently discovered tektites in Brazil are called “geraisites”, after the Brazilian east coast of the state of Minas Gerais where they were found. The gerisites are between 1 gram and 86 grams in mass and have “various shapes”, the researchers wrote, such as spherical or drop-shaped.
They appear black and opaque at first glance, but become grey-green and more transparent when exposed to intense light. The surfaces are marked by cavities, which are bubbles that occurred when the super-hot material was knocked through the atmosphere – much like with lava, a press release noted.
Since the article was published, more geraisites have been found – at least 600 in total. The original discovery zone was in the north of Minas Gerais, including the municipalities of Taiobeiras, Curral de Dentro and São João do Paraíso. But the zone now stretches ten times its original size to 560 miles (900 km) in length, as discoveries were reported in the Brazilian states of Bahia and Piauí.
“This growth in the area of occurrence is completely consistent with what has been observed in other tektite fields around the world. The size of the field depends directly on the energy of the impact, among other factors,” stated the study’s lead author Crósta in the press release.
The geraisites consist mostly of silica (70% to 74%, depending on the sample) along with high concentrations of sodium and potassium oxides. Traces of chromium, nickel and other elements were found, “indicating that the original material was neither pure nor homogeneous”, the press release said.
In some cases, it was what was missing from the rocks that helped researchers find the origin of the tektites. Evidence of an impact comes from inclusions of a type of vitreous silica made only at very high temperatures, known as lechatelierite. The researchers also noted a low water content in the samples, which is characteristic of tektites more generally.
Crósta added that scientists have yet to track down the crater from the impact, but he expected to. This is because of the six mapped fields we now know of, only half of them have a known crater. The crater may have been somewhere in the São Francisco Craton, which is a granitic rock in the eastern part of South America that is one of the oldest regions on the continent. But it will require more study, perhaps using satellite imagery, to see if anything buried or eroded appears in that region.
