Ungrouped Achondrite – ACHON-UNGR; Adrar, Algeria (26°1' 28'' N, 1° 36' 39''W)

Numerous stones featuring distinctive green crystals were found in May 2020 in southern Algeria in the Erg Chech Sand Sea. As they were the only unusually appearing stones on the dunes, the work of meteorite hunters was made easy. No previously known meteorites looked quite like this. Following a battery of tests, as a result of its compositional uniqueness, Erg Chech 002 was classified as an ungrouped achondrite, one of only 116 of 67,000 meteorites in scientific literature. In effect, this meteorite is a sample of a previously unknown and unsampled asteroid.

Less than one year later came the headline news. On March 16, 2021, a research paper published in the Proceedings of the National Academy of Sciences concerning Erg Chech 002 was deemed sufficiently noteworthy that it was shared by hundreds of newspapers throughout the world. Following a result of isotopic analysis, a team of international researchers led by Dr. Jean Alix Barrat determined that Erg Chech 002 meteorites are the oldest volcanic rocks in the solar system — roughly 20 million years older than Earth.

Erg Chech 002 is a volcanic rock from the crust of a protoplanet (an asteroid with an iron core, mantle, crust — and volcanoes) that no longer exists. Surface samples of the oldest protoplanets are virtually unheard of because their parent bodies were typically metamorphosed or destroyed by impacts. The appearance of large pyroxene crystals indicates the magma from which this stone originated must have cooled quite slowly. This pyroxene differs in composition from the pyroxene found on Earth, or that found in other meteorites, because of the relatively high amount of chromium — the same element responsible for emeralds being green. Moreover, the oxygen isotopes of Erg Chech 002 occupy a special niche shared by only four other meteorites, but Erg Chech 002 is mineralogically unlike the other four. (The micrograph of Erg Chech 002, Image 3, by Neil Buckland is not part of this lot.)

Erg Chech 002 is a remarkable meteorite, and this particular specimen has an exceptional earthly provenance as well. It is among the larger specimens and images of this very meteorite were used when the National Academy of Sciences announced its findings. As a result, the article published by scores of newspapers as well as websites throughout the world — including LiveScience, Vice, Forbes and National Geographic — featured an image of the very specimen now offered.

The cut and polished face of this specimen features a variegated warm-hued matrix with large green pyroxene crystals scattered throughout. A prominent vug is seen at the upper perimeter. The soft, undulating curves of the reverse outer surface are also embellished with the same, large emerald-hued crystals. This is a notable offering of a preeminent specimen of the oldest known lava in the solar system.

Christie's would like to thank Dr. Alan E. Rubin at the Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles for his assistance in preparing this catalogue.

159 x 133 x 21mm (6.25 x 5.25 x 0.75 in.) and 605.4g (1.33 lbs)