The findings were detailed in the journal Geology by a research team led by Álvaro Penteado Crósta, a geologist and senior professor at the Institute of Geosciences at the State University of Campinas (IG-UNICAMP). The project involved collaborators from Brazil, Europe, the Middle East, and Australia.

Before this discovery, only five major tektite fields were known worldwide, located in Australasia, Central Europe, the Ivory Coast, North America, and Belize. The Brazilian field now joins this rare group.

A 900 Kilometer Strewn Field of Impact Glass

The geraisites were first documented in three municipalities in northern Minas Gerais — Taiobeiras, Curral de Dentro, and São João do Paraíso — across an area about 90 kilometers long. After the study was submitted, additional finds were reported in Bahia and later in Piauí. As a result, the total known distribution now stretches more than 900 kilometers.

“This growth in the area of occurrence is entirely consistent with what is observed in other tektite fields around the world. The size of the field depends directly on the energy of the impact, among other factors,” Crósta explains.

By July 2025, researchers had collected about 500 pieces. With more recent discoveries, that total now exceeds 600. The fragments vary widely in size, from less than 1 gram to 85.4 grams, and can measure up to 5 centimeters along their longest dimension. Their forms match the aerodynamic shapes typical of tektites, including spheres, ellipsoids, droplets, disks, dumbbells, and twisted shapes.

What the Geraisites Look Like

At first glance, the geraisites appear black and opaque. Under strong light, however, they become translucent with a grayish green hue. This shade differs from the brighter green moldavites of Europe, which have been used in jewelry since the Middle Ages. The surfaces of the Brazilian specimens are pitted with small cavities.

“These small cavities are traces of gas bubbles that escaped during the rapid cooling of the molten material as it traveled through the atmosphere, a process also observed in volcanic lava but especially characteristic of tektites,” says Crósta.

Chemical Clues Confirm Impact Origin

Laboratory analysis shows that the geraisites contain high levels of silica (SiO2), ranging from 70.3% to 73.7%. Sodium (Na2O) and potassium (K2O) oxides together account for 5.86% to 8.01%, slightly higher than what is seen in other tektite regions. Trace elements such as chromium (10-48 parts per million) and nickel (9-63 ppm) vary in small amounts, suggesting the original target rock was not uniform. Researchers also detected rare inclusions of lechatelierite, a high temperature glassy silica that forms during extreme heating, further confirming an impact origin.

“One of the decisive criteria for classifying the material as a tektite was its very low water content, as measured by infrared spectroscopy: between 71 and 107 ppm. For comparison, volcanic glasses, such as obsidian, usually contain from 700 ppm to 2% water, whereas tektites are notoriously much drier,” Crósta points out.

Dating the Ancient Asteroid Impact

Argon isotope dating (⁴⁰Ar/³⁹Ar) indicates the impact occurred around 6.3 million years ago, near the end of the Miocene epoch. Three closely grouped age results were obtained (6.78 ± 0.02 Ma, 6.40 ± 0.02 Ma, and 6.33 ± 0.02 Ma), supporting the conclusion that they came from a single event.

“The age of 6.3 million years should be interpreted as a maximum age since some of the argon may have been inherited from the ancient rocks targeted by the impact,” the researcher comments.

The Search for a Missing Crater

No crater linked to the impact has yet been identified. According to Crósta, this is not unusual. Only three of the six major classical tektite fields have confirmed craters. In the case of the vast Australasia field, the crater is thought to lie beneath the ocean.

Isotopic geochemistry suggests the molten material came from Archean continental crust dating between 3.0 and 3.3 billion years old. That evidence points to the São Francisco craton, one of the oldest and most stable regions of South America’s continental crust.

“The isotopic signature indicates a very ancient continental, granitic source rock. This greatly reduces the universe of candidate areas,” says Crósta.

Future surveys using magnetic and gravimetric techniques could detect circular underground structures that mark a buried or eroded crater.

Estimating the Size of the Impact

Researchers cannot yet determine the exact size of the object that struck Earth, but they believe it was not small. The volume of melted rock and the broad distribution of debris indicate a powerful event, though likely less intense than the impact that created the enormous Australasia field, which spans thousands of kilometers.

The team is developing mathematical models to estimate the impact’s energy, entry speed, trajectory angle, and total volume of melted material. These calculations will become more refined as additional data on the distribution of geraisites are gathered.

The discovery adds an important chapter to South America’s impact history. Only about nine large impact structures are currently known on the continent, most of them much older and located in Brazil. The findings also suggest that tektites may be more widespread than previously recognized, but are sometimes overlooked or mistaken for ordinary glass.

Separating Science From Speculation

To address exaggerated claims about asteroid threats, Crósta works with undergraduate students to manage the Instagram account @defesaplanetaria. The page focuses on science communication and aims to distinguish genuine risks from unfounded speculation about meteorites and asteroids.

Impacts were common in the early solar system, when debris was abundant and planetary orbits were unstable. Large bodies shifted positions, sending smaller objects in many directions. Today, the solar system is far more stable, and major impacts are much less frequent.

“Understanding these processes is essential to separating science from speculation,” the researcher concludes.

Crósta has studied meteorite impact structures since his master’s research project in 1978. Over the years, he has received several grants from FAPESP (08/53588-7, 12/50368-1, and 12/51318-8).

To make the product, the team used honey from native bees as a natural, edible solvent to draw out beneficial compounds from cocoa shells, a byproduct typically discarded during chocolate production. These compounds include theobromine and caffeine, which are linked to heart health. The ultrasound-assisted process also boosted the honey’s levels of phenolic compounds, known for their antioxidant and anti-inflammatory effects.

Researchers who sampled the mixture report a pronounced chocolate flavor that varies depending on the proportion of honey to cocoa shells. Additional testing is planned to further evaluate taste and other sensory characteristics.

“Of course, the biggest appeal to the public is the flavor, but our analyses have shown that it has a number of bioactive compounds that make it quite interesting from a nutritional and cosmetic point of view,” says Felipe Sanchez Bragagnolo, the study’s first author. He carried out the research during his postdoctoral work at the Faculty of Applied Sciences (FCA) at UNICAMP in Limeira with support from FAPESP.

Working with INOVA UNICAMP, the university’s innovation agency, the team is now seeking a commercial partner to license the patented method and bring the product to market (read more at agencia.fapesp.br/52969).

Native Bee Honey and Biodiversity

Beyond reducing food waste, the project highlights the sustainable use of local biodiversity. Honey from native Brazilian bees was selected because it generally contains more water and is less viscous than honey from European bees (Apis mellifera), making it more effective for extracting compounds.

The researchers tested honey from five Brazilian species: borá (Tetragona clavipes), jataí (Tetragonisca angustula), mandaçaia (Melipona quadrifasciata), mandaguari (Scaptotrigona postica), and moça-branca (Frieseomelitta varia). Cocoa shells were supplied by the São Paulo State Department of Agriculture and Supply’s Comprehensive Technical Assistance Coordination Office (CATI) unit in São José do Rio Preto.

Mandaguari honey was initially used to refine the extraction process because its water content and viscosity were moderate compared to the others. Once optimized, the same procedure was applied to the remaining honey varieties.

Bragagnolo notes that honey is sensitive to environmental factors such as climate, storage, and temperature. “Therefore, it’s possible to adapt the process to locally available honey, not necessarily mandaguari honey,” he says.

Green Chemistry and Ultrasound Extraction

The extraction method relies on ultrasound technology. A probe that resembles a metal pen is inserted into a container holding the honey and cocoa shells. Sound waves generated by the probe help release compounds from the plant material so they dissolve into the honey.

This approach works by forming microscopic bubbles that collapse and briefly raise the temperature, helping break down the shells. In the food industry, ultrasound-assisted extraction is viewed as an environmentally friendly technique because it is faster and more efficient than many conventional methods.

Sustainability was formally evaluated in the study using Path2Green software, developed by a team led by Professor Mauricio Ariel Rostagno of FCA-UNICAMP, who also supervised Bragagnolo’s postdoctoral research and coordinated the project. The analysis measured how well the process aligned with 12 principles of green chemistry, including transportation, post-treatment, purification, and application. The use of a local, edible, ready-to-use solvent was a major advantage. On a scale of -1 to +1, the product received a score of +0.118.

“We believe that with a device like this, in a cooperative or small business that already works with both cocoa and native bee honey, it’d be possible to increase the portfolio with a value-added product, including for haute cuisine,” Rostagno suggests.

Shelf Life and Future Applications

The team is also planning studies to examine how ultrasound affects honey microbiology. Just as it breaks down plant cells, ultrasound can disrupt the cell walls of microorganisms such as bacteria that may spoil the product.

“Honey from native bees usually needs to be refrigerated, matured, dehumidified, or pasteurized, unlike honey from European bees, which can be stored at room temperature. We suspect that, simply by being exposed to ultrasound, the microorganisms contained in the honey are eliminated, increasing the stability and shelf life of the product,” he explains.

Looking ahead, the researchers intend to explore other uses for native bee honey as a solvent in ultrasound-assisted extraction, including processing additional plant residues.

Along with postdoctoral fellowships and an international research internship for Bragagnolo, the project received multiple scholarships and grants from FAPESP (23/02064-8, 23/16744-0, 21/12264-9, 20/08421-9, 19/13496-0, and 18/14582-5.

Using an advanced light based imaging method combined with machine learning, the team examined brain tissue from both healthy and Alzheimer’s affected animals. Their results, published in ACS Applied Materials and Interfaces, reveal that chemical changes linked to Alzheimer’s are not confined to amyloid plaques. Instead, these alterations appear throughout the brain in uneven and complex patterns.

Laser Imaging Reveals Brain Chemistry in Detail

To detect these subtle shifts, the scientists turned to hyperspectral Raman imaging. This sophisticated form of Raman spectroscopy uses a laser to detect the unique chemical fingerprints of molecules within tissue.

“Traditional Raman spectroscopy takes one measurement of chemical information per molecular site,” said Ziyang Wang, an electrical and computer engineering doctoral student at Rice who is a first author on the study. “Hyperspectral Raman imaging repeats this measurement thousands of times across an entire tissue slice to build a full map. The result is a detailed picture showing how chemical composition varies across different regions of the brain.”

The researchers scanned entire brains slice by slice, compiling thousands of overlapping measurements to build high resolution molecular maps of both healthy and diseased tissue. Because the imaging was label free, the samples were not treated with dyes, fluorescent proteins or molecular tags.

“This means we observed the brain as is, capturing a complete, unaltered portrait of its chemical makeup,” Wang said. “I think this makes the approach more unbiased and better suited for discovering new disease-related changes that might otherwise be missed.”

Machine Learning Maps Uneven Alzheimer’s Damage

The imaging process generated enormous amounts of data, which the team analyzed using machine learning (ML). They first applied unsupervised ML, allowing algorithms to detect natural patterns in the chemical signals without prior assumptions. These models sorted tissue based entirely on its molecular characteristics. The researchers then used supervised ML, training models to distinguish between Alzheimer’s and non Alzheimer’s samples. This step helped determine how strongly different brain regions reflected Alzheimer’s related chemistry.

“We found that the changes caused by Alzheimer’s disease are not spread evenly across the brain,” Wang said. “Some regions show strong chemical changes, while others are less affected. This uneven pattern helps explain why symptoms appear gradually and why treatments that focus on only one problem have had limited success.”

Metabolic Disruption in Memory Regions

Beyond protein buildup, the study identified broader metabolic differences between healthy and Alzheimer’s brains. Levels of cholesterol and glycogen varied across regions, with the most dramatic contrasts appearing in areas responsible for memory, particularly the hippocampus and cortex.

“Cholesterol is important for maintaining brain cell structure, and glycogen serves as a local energy reserve,” said Shengxi Huang, associate professor of electrical and computer engineering and materials science and nanoengineering and corresponding author on the study. “Together, these findings support the idea that Alzheimer’s involves broader disruptions in brain structure and energy balance, not only protein buildup and misfolding,” added Huang, who is also a member of the Ken Kennedy Institute, the Rice Advanced Materials Institute and the Smalley-Curl Institute.

A Broader View of Alzheimer’s Progression

The project grew out of ongoing discussions about new ways to study the Alzheimer’s brain.

“At first, we were measuring only small areas of brain tissue,” Wang said. “Then I thought, what if we could map the entire brain and gain a much broader view? It took several rounds of testing and trial and error before the measurements and analysis worked well together.”

When the complete chemical map finally came together, the impact was immediate.

“Patterns emerged that had not been visible under regular imaging,” Wang said. “Seeing those results was deeply satisfying. It felt like revealing a hidden layer of information that had been there all along, waiting for the right way to be analyzed.”

By delivering the first detailed, dye free chemical maps of the Alzheimer’s brain, this research offers a more comprehensive view of the disease. The team hopes the findings will eventually support earlier diagnosis and more effective strategies to slow progression.

The research was supported by the National Science Foundation (2246564, 1934977), the National Institutes of Health (1R01AG077016) and the Welch Foundation (C2144).