Meteorite from El Ali, Hiiraan, Somalia (2020) 9th largest - 15 tonne

A team of researchers has discovered at least two new minerals that have never before been seen on Earth in a 15 tonne meteorite found in Somalia — the ninth largest meteorite ever found.

“Whenever you find a new mineral, it means that the actual geological conditions, the chemistry of the rock, was different than what’s been found before,” says Chris Herd, a professor in the Department of Earth & Atmospheric Sciences and curator of the University of Alberta’s Meteorite Collection. “That’s what makes this exciting: In this particular meteorite you have two officially described minerals that are new to science.”

The two minerals found came from a single 70 gram slice that was sent to the U of A for classification, and there already appears to be a potential third mineral under consideration. If researchers were to obtain more samples from the massive meteorite, there’s a chance that even more might be found, Herd notes.

The two newly discovered minerals have been named elaliite and elkinstantonite.

In collaboration with researchers at UCLA and the California Institute of Technology, Herd classified the El Ali meteorite as an “Iron, IAB complex” meteorite, one of over 350 in that particular category.

As Herd was analyzing the meteorite to classify it, he saw something that caught his attention. He brought in the expertise of Andrew Locock, head of the U of A’s Electron Microprobe Laboratory, who has been involved in other new mineral descriptions including Heamanite-(Ce).

“Phosphates in iron meteorites are secondary products: They form through oxidation of phosphides … which are rare primary components of iron meteorites,” he said via email. “Hence, the two new phosphates tell us about oxidation processes that occurred in the meteorite material. It remains to be seen if the oxidation occurred in space or on Earth, after the fall, but as far as I know, many of these meteorite phosphates formed in space. In either case, water is probably the reactant that caused the oxidation.”

The location of the main mass of the meteorite is uncertain; it was last recorded being shipped to China, presumably for sale. Small samples are held at the University of Arizona, the University of Alberta, and UC Los Angeles.

The IAB meteorites are composed of meteoric iron (kamacite and taenite) and silicate inclusions. Structurally they can be hexahedrites, fine to coarse octahedrites, or even ataxites. Most of them are octahedrite with medium to coarse taenite-lamella and distinct Widmanstätten patterning.

The silicate inclusions are composed of low-Ca pyroxene, high-Ca pyroxene, olivine, plagioclase, troilite, graphite, different phosphates, meteoric iron and traces of daubréelite and chromite.

Astronuc said:

I wonder if the minerals formed during the descent through the atmosphere or upon impact.