Geologists discover Brazil's first tektite field following massive asteroid impact six million years ago

Scientists uncover a 900-kilometer field of "geraisites" in Brazil, identifying a major asteroid impact that occurred 6.3 million years ago.

By: AXL Media

Published: Mar 2, 2026, 11:18 AM EST

Source: The information in this article was sourced from ScienceDaily

Identification of Brazil's First Tektite Field

A research team led by Álvaro Penteado Crósta from the State University of Campinas has documented the first known field of tektites in Brazil. Tektites are natural glass fragments created when an extraterrestrial object impacts the Earth with enough force to melt terrestrial rock and eject it into the atmosphere. This discovery, detailed in the journal Geology, places Brazil among a rare group of global locations possessing major tektite fields, including sites in North America, Central Europe, and Australasia.

Geographic Distribution of Geraisites

The impact glass specimens have been named geraisites in honor of the state of Minas Gerais, where they were initially recovered. While the first samples were found within a 90-kilometer range, subsequent reports in Bahia and Piauí have expanded the known strewn field to over 900 kilometers. Geologists explain that the vast size of this field is a direct indicator of the extreme energy released during the ancient impact event, which occurred near the end of the Miocene epoch.

Physical and Chemical Characteristics

Geraisites typically appear black and opaque, but they reveal a translucent grayish-green color when held under strong light. Researchers have collected over 600 fragments, ranging from less than one gram to over 85 grams. Chemical analysis confirms an impact origin due to high silica content and the presence of lechatelierite, a type of glass that only forms under extreme temperatures. A defining characteristic is the material's exceptionally low water content, which distinguishes it from volcanic glasses like obsidian.