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Ureilite
194 mm x 108 mm x 55 mm
1,769 grams
Ureilite is a rare type of stony meteorite known for its unusual mineralogical makeup compared to most other space rocks. Composed mainly of the silicate minerals olivine and pyroxene, ureilites also contain a significant amount of carbon in the form of nanodiamonds created by intense pressure from cosmic collisions. From the book Meteorites and Their Parent Planets by Harry McSween: 'The ureilites are arguably the most bizarre and perplexing of all meteorites. Filling the spaces between the larger silicate grains is a matrix of graphite or diamond. The coarse-grained size of the ureilites suggest they formed in the deep interior of their parent body. These crystals typically meet in triple junctions and have curved boundaries' (p.145).
This is why you rarely see a cut and polished face of the interior—it took several saw blades to cut through all of the diamondoid in this meteorite! It’s an exotic meteorite, an end cut of the recently classified Ureilite NWA 17786, a single stone found in the Western Sahara in 2024. It has a low weathering and shock grade and is described as a 'coarse-grained ultramafic rock composed of olivine and low-Ca pyroxene (pigeonite) with…considerable amounts of graphite.'
'One of the most interesting characteristics of ureilites is that they have experienced variable but typically intense shock metamorphism…4.0 billion years ago' (McSween, p.147). Truly a blast from the past.
