Collection
Classification: HED achondrite Diogenite
Observed fall: No
Year found: 2013
City, Country: Western Sahara
Mass: 20 kg
In collection
Weight #1 : 4,5 g (fragment lot)
Certificate of authenticity: Yes (1)
NWA 7831 is a Diogenite (DIO) meteorite, part of the HED (Howardite-Eucrite-Diogenite) clan that is strongly linked to asteroid 4 Vesta. Diogenites are composed predominantly of orthopyroxene, and NWA 7831’s coarse-grained, crystalline texture suggests it formed deep within Vesta’s crust or upper mantle. This slow-cooling environment allowed large, well-formed orthopyroxene crystals to grow, often accompanied by minor olivine and chromite inclusions. Studying NWA 7831 provides valuable insights into magmatic processes, thermal evolution, and the internal structure of Vesta—one of the earliest differentiated bodies in the solar system.
When examining a thin section of NWA 7831 – a Diogenite (DIO) meteorite under a light microscope, the field of view is dominated by large, well-formed orthopyroxene crystals, often exhibiting a granular to equigranular texture. Under polarized light, these orthopyroxene grains display low to moderate interference colors and distinct cleavage planes, with straight extinction when rotated. Occasional olivine or chromite inclusions may appear as darker, high-relief grains nestled within the orthopyroxene matrix. Fractures and minor grain boundaries are visible, reflecting the rock’s thermal and impact history. Overall, the microscope reveals a coarse-grained, crystalline texture indicative of slow cooling and magmatic differentiation within the deep crustal or mantle regions of its parent asteroid.
