This group represents the least common class of ordinary chondrites since it includes just about 1,100 members (again, including probable pairings). The "LL" stands for "low iron" and "low metal" reflecting that LL chondrites usually contain a weight percentage of 19 to 22% total iron, but only 1 to 3% free metal. Hence, they are only weakly attracted to a magnet.
Like the other ordinary chondrites, the LL chondrites show petrologic types from 1 - 7, but the distribution of types shows no distinct peak. The most common LL chondrites are LL6 and LL5 with about 400 members each. More unequilibrated types such as LL4 and LL3 are much more rare with just about 70 members each. The olivine in LL chondrites is more iron-rich than in the other ordinary chondrites, and this implies that the LL chondrites must have formed under more oxidizing conditions than the H or L chondrites. Older literature lists the LL chondrites often as "amphoterites" since they were thought to be a connecting link between chondrites and achondrites, but this name is misleading and no longer in use.
Scientists are still searching for a probable parent body for the LL group. One small main belt asteroid, 3628 Boznemcová, has been spotted which exhibits a similar reflectance spectrum to the spectra of the LL chondrites, but with a diameter of just 7 km it seems to be too small to be regarded as the original parent body of the LL members. Maybe it's just a fragment of a common ancestor which links the LL chondrites to 3628 Boznemcová, and further research will still have to find the real source of the LL chondrites within the dense population of NEOs crossing Earth's orbit.
