Collection
Classification: Ordinary (O) LL4-7 (Low iron Low metal) chondrite
Observed fall: No
Year found: 2013
City, Country: Northwest Africa
Mass: 250 g
In collection
Weight #1 : 3,84 g
Certificate of authenticity: Yes (1)
LL chondrites are a type of ordinary chondrite characterized by low iron (Low Fe) and low metal content, with most of their iron present in silicate minerals like olivine and pyroxene rather than in metallic form. The petrologic types 4 to 7 indicate varying degrees of thermal metamorphism, with higher numbers representing greater metamorphic alteration. NWA 10267 exhibits a range of metamorphic grades within the same specimen. This means it contains regions that have experienced different levels of heating on its parent asteroid, transitioning from well-preserved chondritic textures (type 4) to highly metamorphosed and recrystallized areas (up to type 7).
When examining a LL4-7 (Low iron Low metal) meteorite under a light microscope, several distinctive features can be observed:
several features indicative of varying degrees of thermal metamorphism become apparent. In the LL4 regions, you can observe well-defined chondrules composed primarily of olivine and orthopyroxene, with some minor recrystallization beginning to blur their boundaries. These chondrules exhibit distinct textures such as porphyritic, barred olivine, and radial pyroxene types. As you progress to higher metamorphic grades (LL5 to LL6), the chondrules become increasingly indistinct due to extensive recrystallization; their boundaries are blurred, and the matrix transforms into a more equigranular texture. In the highest grade areas (LL7), chondrules are almost entirely obliterated, resulting in a uniformly recrystallized assemblage of olivine and pyroxene grains. Throughout the sample, metallic iron-nickel grains are sparse due to the low metal content characteristic of LL chondrites, and most iron is incorporated within silicate minerals rather than existing as separate metal phases.
