In 1996, an archaeologist named Aly A. Barakat was doing fieldwork in an Egyptian desert and stumbled across an unusual shiny black pebble now known as the Hypatia stone (after Hypatia of Alexandria). The stone’s origin is unknown, but several years of research have shown that it has been proven. And according to a recent paper published in the journal Icarus, the stone’s parent body was likely born in the aftermath of a rare type Ia supernova explosion.
The Hypatia Stone was discovered in southwest Egypt, a region known for its Libyan Desert Glass. This glass is thought to have been formed by an extreme heating event or a meteorite. Although the impact may have been involved, evidence is more consistent with a comet as the parent body.
Jan Kramers, University of Johannesburg’s chief scientist, and his colleagues have been studying the Hypatia Stone for many years. Kramers likened the Hypatia stone’s internal structure to a fruitcake. A poorly mixed dough forms the bulk of the Hypatia stone (mixed matrixes), while the minerals grains hiding in the stone’s inclusions represent the cherries and the nuts. Kramers compared the secondary substances found in the stone’s cracks with the flour that fills in the gaps in a fruitcake.
In 2013 Kramers and colleagues published the results of a chemical analysis that provided strong evidence in favor of the stone being a comet fragment. This was an interesting suggestion, as most of the comet fragments on Earth are made up of microscopic dust particles found in the upper atmosphere or buried under Antarctic ice. The comet hypothesis would explain the presence of microscopic diamonds in the stone, likely formed in the impact when the comet exploded above Egypt some 28.5 million years ago. (The presence of those micro-diamonds is probably why the stone managed to make it to Earth without disintegrating)
However, work by other research teams in 2015 ruled out a comet or meteorite as the stone’s source, based on noble gas and nuclear probe analyses. It doesn’t look like the mineral matrix of known meteorites. For example, it contains a lot of carbon and very little silicon. It’s unlikely that it came from Earth.
Kramers et al. ‘s 2018 micro-mineral analysis revealed that the matrix also has a high concentration of polyaromatic hydrocarbons (PAH)–a major component of interstellar dust–and those microscopic diamonds. These grains were composed of aluminum, silver, phosphide and silicon carbide. Very little iron was found. These elements are the main constituents of most rocky planets. Kramers and his coworkers concluded that the Hypatia rock contained matter that existed before our Solar System was formed.