HED achondrite (Diogenite)
Found in Northwest Africa, 2022
Beautiful rock from Asteroid Vesta, or as recently thought a Vestoid (asteroid similar to Vesta). Diogenites are thought to be of plutonic origin. In both terrestrial and extraterrestrial geology, plutonic rocks are intrusive igneous rocks. That means they were once lava, but instead of being thrown out by a volcano and cooling on the surface, they cooled slowly underground. Slow cooling means they had time to grow large crystals which are often green in color.
Only a single 6.2 kilogram stone of NWA 15953 was found by an Algerian dealer in 2022, and these complete laboratory-prepared slices were taken from it. It has been classified by Diogenite (annealed monomict breccia) by A. Irving of UWS and J. Boesenberg, Brown University. They describe it as having, “Annealed breccia composed of larger angular grains (up to 5mm) of orthopyroxene within a finer grained matrix of interlocking orthopyroxene grains accompanied by small grains (~50 µm) of olivine, chromite, troilite and Ni-poor kamacite inclusions. All orthopyroxene exhibits undulose extinction.”