Recommended classes in the Meteoritical Bulletin Database are assigned by the database editor. In most cases, this is based on the most recent classification that appears in either the Catalogue of Meteorites, MetBase, the US Antarctic Meteorite Newsletter, the Japanese Meteorite Newsletter, or the Meteoritical Bulletin. However, in a few cases it reflects differences of opinion about the proper way to classify the meteorite. The nomenclature used may also be modified by the editor to conform to an internally consistent classification scheme
The recommended classification EH3/4-an means:
"An enstatite chondrite of the EH group that is either petrologic type 3 or type 4 and has anomalous properties."
The highlighted words are defined as follows:
enstatite chondrite: A major class of chondrites that mostly have sub-solar Mg/Si and refractory/Si ratios, oxygen isotope compositions that plot near the terrestrial fractionation line, and highly reduced mineral assemblages (containing little FeO, Si-bearing metal, and sulfides of elements normally considered lithophile).
EH group: The high-iron (EH) chemical group of enstatite chondrites, distinguished by small chondrules (0.2 mm), abundant metal (~10 vol%) that is rich in Si (~3 wt%), and an extremely reduced mineral assemblage including niningerite (MgS) and perryite (Fe-Ni silicide).
type 3: Designates chondrites that are characterized by abundant chondrules, low degrees of aqueous alteration, and unequilibrated mineral assemblages. Many of the low-Ca pyroxene grains are monoclinic and exhibit polysynthetic twinning. The type 3 chondrites may be divided into subtypes ranging from 3.00 (least metamorphosed) to 3.9 (nearly metamorphosed to type 4 levels). If primary igneous glass occurs in the chondrules, it belongs to type 3.
type 4: Designates chondrites that are characterized by abundant chondrules, and have been metamorphosed under conditions sufficient to homogenize olivine compositions and recrystallize fine-grained matrix. Some of the low-Ca pyroxene grains may be monoclinic and exhibit polysynthetic twinning. Primary igneous chondrule glass is absent.
anomalous: Designates meteorites that have been determined to be a member of a specific group, but have certain properties that are unusual or distinctive.
Find all meteorites of type: EH3/4-an