Black Diamonds, Meteorites and the Mystery of Carbonado
A public, expanded version of a newsletter article.
Carbonado, the porous black "diamond" that collectors sometimes call "carbon auto," is still a puzzle. This is a background piece with one recent study.
A 2026 study
A 2026 paper in Gondwana Research studied carbonados from Chapada Diamantina in Brazil. Its authors report that carbonados occur in alluvial sediments in Brazil and Central Africa, are Archean in age (billions of years old), and have a glassy outer surface and many small pores. They found no shock features inside the grains and concluded that an impact origin is ruled out. They propose that an impact may have driven organic material deep into the mantle, where porous diamond formed.
The meteorite idea
In 2006, researchers at Florida International University and Case Western Reserve used infrared light at Brookhaven National Laboratory and argued that carbonado came from outer space. That claim is contested, and a 2024 review in Minerals says carbonado's origin is still unknown.
Diamonds that really do come from meteorites
A 2026 study in Carbon examined diamond in fragments of the Almahata Sitta meteorite and found features it interprets as shock from impacts on the parent body. It also notes that the mineral name "lonsdaleite," first reported in Canyon Diablo material, may describe disordered ordinary diamond rather than a distinct form.
Frequently asked questions
Is carbonado from space? Not settled. The 2026 study argues against an impact origin, and a 2024 review says the origin is unknown.
Are there diamonds in meteorites? Yes. The 2026 Carbon study looked at diamond in Almahata Sitta fragments.
Is carbonado valuable? We did not research prices, so we make no claim.
Sources
Every fact above comes from one of these sources, read in October 2026. Details may have changed since.
- Gondwana Research, 2026: https://doi.org/10.1016/j.gr.2026.03.010
- Brookhaven National Laboratory: https://www.bnl.gov/newsroom/news.php?a=110576
- Astrophysical Journal Letters, 2006: https://iopscience.iop.org/article/10.1086/510451
- Minerals, 2024: https://www.mdpi.com/2075-163X/14/9/927
- Carbon, 2026: https://doi.org/10.1016/j.carbon.2026.122098
- PNAS, 2020: https://www.pnas.org/doi/10.1073/pnas.1919067117
Drafted October 18, 2026 from Issue 1002. Spotted an error? Email asadigitalart000@gmail.com and we will fix it.
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